Upload llama.cpp/ggml/src/ggml-rpc.cpp with huggingface_hub

llama.cpp/ggml/src/ggml-rpc.cpp

@@ -0,0 +1,1403 @@
+#include "ggml-rpc.h"
+#include "ggml-impl.h"
+#include "ggml-backend-impl.h"
+
+#include <cinttypes>
+#include <string>
+#include <vector>
+#include <memory>
+#include <mutex>
+#include <unordered_map>
+#include <unordered_set>
+#ifdef _WIN32
+#  define WIN32_LEAN_AND_MEAN
+#  ifndef NOMINMAX
+#     define NOMINMAX
+#  endif
+#  include <windows.h>
+#  include <winsock2.h>
+#else
+#  include <arpa/inet.h>
+#  include <sys/socket.h>
+#  include <sys/types.h>
+#  include <netinet/in.h>
+#  include <netinet/tcp.h>
+#  include <netdb.h>
+#  include <unistd.h>
+#endif
+#include <cstring>
+
+#define UNUSED GGML_UNUSED
+
+#define GGML_DEBUG 0
+#if (GGML_DEBUG >= 1)
+#define GGML_PRINT_DEBUG(...) printf(__VA_ARGS__)
+#else
+#define GGML_PRINT_DEBUG(...)
+#endif
+
+#ifdef _WIN32
+typedef SOCKET sockfd_t;
+using ssize_t = __int64;
+#else
+typedef int sockfd_t;
+#endif
+
+// cross-platform socket
+struct socket_t {
+    sockfd_t fd;
+    socket_t(sockfd_t fd) : fd(fd) {}
+    ~socket_t() {
+        GGML_PRINT_DEBUG("[%s] closing socket %d\n", __func__, this->fd);
+#ifdef _WIN32
+        closesocket(this->fd);
+#else
+        close(this->fd);
+#endif
+    }
+};
+
+// all RPC structures must be packed
+#pragma pack(push, 1)
+// ggml_tensor is serialized into rpc_tensor
+struct rpc_tensor {
+    uint64_t id;
+    uint32_t type;
+    uint64_t buffer;
+    uint32_t ne[GGML_MAX_DIMS];
+    uint32_t nb[GGML_MAX_DIMS];
+    uint32_t op;
+    int32_t  op_params[GGML_MAX_OP_PARAMS / sizeof(int32_t)];
+    int32_t  flags;
+    uint64_t src[GGML_MAX_SRC];
+    uint64_t view_src;
+    uint64_t view_offs;
+    uint64_t data;
+    char name[GGML_MAX_NAME];
+
+    char padding[4];
+};
+
+static_assert(sizeof(rpc_tensor) % 8 == 0, "rpc_tensor size must be multiple of 8");
+
+// RPC commands
+enum rpc_cmd {
+    RPC_CMD_ALLOC_BUFFER = 0,
+    RPC_CMD_GET_ALIGNMENT,
+    RPC_CMD_GET_MAX_SIZE,
+    RPC_CMD_BUFFER_GET_BASE,
+    RPC_CMD_FREE_BUFFER,
+    RPC_CMD_BUFFER_CLEAR,
+    RPC_CMD_SET_TENSOR,
+    RPC_CMD_GET_TENSOR,
+    RPC_CMD_COPY_TENSOR,
+    RPC_CMD_GRAPH_COMPUTE,
+    RPC_CMD_GET_DEVICE_MEMORY,
+    RPC_CMD_COUNT,
+};
+
+struct rpc_msg_alloc_buffer_req {
+    uint64_t size;
+};
+
+struct rpc_msg_alloc_buffer_rsp {
+    uint64_t remote_ptr;
+    uint64_t remote_size;
+};
+
+struct rpc_msg_get_alignment_rsp {
+    uint64_t alignment;
+};
+
+struct rpc_msg_get_max_size_rsp {
+    uint64_t max_size;
+};
+
+struct rpc_msg_buffer_get_base_req {
+    uint64_t remote_ptr;
+};
+
+struct rpc_msg_buffer_get_base_rsp {
+    uint64_t base_ptr;
+};
+
+struct rpc_msg_free_buffer_req {
+    uint64_t remote_ptr;
+};
+
+struct rpc_msg_buffer_clear_req {
+    uint64_t remote_ptr;
+    uint8_t value;
+};
+
+struct rpc_msg_get_tensor_req {
+    rpc_tensor tensor;
+    uint64_t offset;
+    uint64_t size;
+};
+
+struct rpc_msg_copy_tensor_req {
+    rpc_tensor src;
+    rpc_tensor dst;
+};
+
+struct rpc_msg_copy_tensor_rsp {
+    uint8_t result;
+};
+
+struct rpc_msg_graph_compute_rsp {
+    uint8_t result;
+};
+
+struct rpc_msg_get_device_memory_rsp {
+    uint64_t free_mem;
+    uint64_t total_mem;
+};
+#pragma pack(pop)
+
+// RPC data structures
+
+static ggml_guid_t ggml_backend_rpc_guid() {
+    static ggml_guid guid = {0x99, 0x68, 0x5b, 0x6c, 0xd2, 0x83, 0x3d, 0x24, 0x25, 0x36, 0x72, 0xe1, 0x5b, 0x0e, 0x14, 0x03};
+    return &guid;
+}
+
+struct ggml_backend_rpc_buffer_type_context {
+    std::string endpoint;
+    std::string name;
+    size_t alignment;
+    size_t max_size;
+};
+
+struct ggml_backend_rpc_context {
+    std::string endpoint;
+    std::string name;
+};
+
+struct ggml_backend_rpc_buffer_context {
+    std::shared_ptr<socket_t> sock;
+    std::unordered_map<ggml_backend_buffer_t, void *> base_cache;
+    uint64_t remote_ptr;
+};
+
+// RPC helper functions
+
+static std::shared_ptr<socket_t> make_socket(sockfd_t fd) {
+#ifdef _WIN32
+    if (fd == INVALID_SOCKET) {
+        return nullptr;
+    }
+#else
+    if (fd < 0) {
+        return nullptr;
+    }
+#endif
+    return std::make_shared<socket_t>(fd);
+}
+
+static bool set_no_delay(sockfd_t sockfd) {
+    int flag = 1;
+    // set TCP_NODELAY to disable Nagle's algorithm
+    int ret = setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, (char *)&flag, sizeof(int));
+    return ret == 0;
+}
+
+static bool set_reuse_addr(sockfd_t sockfd) {
+    int flag = 1;
+    int ret = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, (char *)&flag, sizeof(int));
+    return ret == 0;
+}
+
+static std::shared_ptr<socket_t> socket_connect(const char * host, int port) {
+    struct sockaddr_in addr;
+    auto sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    auto sock_ptr = make_socket(sockfd);
+    if (sock_ptr == nullptr) {
+        return nullptr;
+    }
+    if (!set_no_delay(sockfd)) {
+        fprintf(stderr, "Failed to set TCP_NODELAY\n");
+        return nullptr;
+    }
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons(port);
+    struct hostent * server = gethostbyname(host);
+    if (server == NULL) {
+        fprintf(stderr, "Cannot resolve host '%s'\n", host);
+        return nullptr;
+    }
+    memcpy(&addr.sin_addr.s_addr, server->h_addr, server->h_length);
+    if (connect(sock_ptr->fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
+        return nullptr;
+    }
+    return sock_ptr;
+}
+
+static std::shared_ptr<socket_t> socket_accept(sockfd_t srv_sockfd) {
+    auto client_socket_fd = accept(srv_sockfd, NULL, NULL);
+    auto client_socket = make_socket(client_socket_fd);
+    if (client_socket == nullptr) {
+        return nullptr;
+    }
+    if (!set_no_delay(client_socket_fd)) {
+        fprintf(stderr, "Failed to set TCP_NODELAY\n");
+        return nullptr;
+    }
+    return client_socket;
+}
+
+static std::shared_ptr<socket_t> create_server_socket(const char * host, int port) {
+    auto sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    auto sock = make_socket(sockfd);
+    if (sock == nullptr) {
+        return nullptr;
+    }
+    if (!set_reuse_addr(sockfd)) {
+        fprintf(stderr, "Failed to set SO_REUSEADDR\n");
+        return nullptr;
+    }
+    if (inet_addr(host) == INADDR_NONE) {
+        fprintf(stderr, "Invalid host address: %s\n", host);
+        return nullptr;
+    }
+    struct sockaddr_in serv_addr;
+    serv_addr.sin_family = AF_INET;
+    serv_addr.sin_addr.s_addr = inet_addr(host);
+    serv_addr.sin_port = htons(port);
+
+    if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
+        return nullptr;
+    }
+    if (listen(sockfd, 1) < 0) {
+        return nullptr;
+    }
+    return sock;
+}
+
+static bool send_data(sockfd_t sockfd, const void * data, size_t size) {
+    size_t bytes_sent = 0;
+    while (bytes_sent < size) {
+        ssize_t n = send(sockfd, (const char *)data + bytes_sent, size - bytes_sent, 0);
+        if (n < 0) {
+            return false;
+        }
+        bytes_sent += n;
+    }
+    return true;
+}
+
+static bool recv_data(sockfd_t sockfd, void * data, size_t size) {
+    size_t bytes_recv = 0;
+    while (bytes_recv < size) {
+        ssize_t n = recv(sockfd, (char *)data + bytes_recv, size - bytes_recv, 0);
+        if (n <= 0) {
+            return false;
+        }
+        bytes_recv += n;
+    }
+    return true;
+}
+
+static bool send_msg(sockfd_t sockfd, const void * msg, size_t msg_size) {
+    if (!send_data(sockfd, &msg_size, sizeof(msg_size))) {
+        return false;
+    }
+    return send_data(sockfd, msg, msg_size);
+}
+
+static bool recv_msg(sockfd_t sockfd, void * msg, size_t msg_size) {
+    uint64_t size;
+    if (!recv_data(sockfd, &size, sizeof(size))) {
+        return false;
+    }
+    if (size != msg_size) {
+        return false;
+    }
+    return recv_data(sockfd, msg, msg_size);
+}
+
+static bool recv_msg(sockfd_t sockfd, std::vector<uint8_t> & input) {
+    uint64_t size;
+    if (!recv_data(sockfd, &size, sizeof(size))) {
+        return false;
+    }
+    try {
+        input.resize(size);
+    } catch (const std::bad_alloc & e) {
+        fprintf(stderr, "Failed to allocate input buffer of size %" PRIu64 "\n", size);
+        return false;
+    }
+    return recv_data(sockfd, input.data(), size);
+}
+
+static bool parse_endpoint(const std::string & endpoint, std::string & host, int & port) {
+    size_t pos = endpoint.find(':');
+    if (pos == std::string::npos) {
+        return false;
+    }
+    host = endpoint.substr(0, pos);
+    port = std::stoi(endpoint.substr(pos + 1));
+    return true;
+}
+
+// RPC request : | rpc_cmd (1 byte) | request_size (8 bytes) | request_data (request_size bytes) |
+// RPC response: | response_size (8 bytes) | response_data (response_size bytes) |
+static bool send_rpc_cmd(const std::shared_ptr<socket_t> & sock, enum rpc_cmd cmd, const void * input, size_t input_size, void * output, size_t output_size) {
+    uint8_t cmd_byte = cmd;
+    if (!send_data(sock->fd, &cmd_byte, sizeof(cmd_byte))) {
+        return false;
+    }
+    if (!send_data(sock->fd, &input_size, sizeof(input_size))) {
+        return false;
+    }
+    if (!send_data(sock->fd, input, input_size)) {
+        return false;
+    }
+    // TODO: currently the output_size is always known, do we need support for commands with variable output size?
+    // even if we do, we can skip sending output_size from the server for commands with known output size
+    uint64_t out_size;
+    if (!recv_data(sock->fd, &out_size, sizeof(out_size))) {
+        return false;
+    }
+    if (out_size != output_size) {
+        return false;
+    }
+    if (!recv_data(sock->fd, output, output_size)) {
+        return false;
+    }
+    return true;
+}
+
+// RPC client-side implementation
+
+static std::shared_ptr<socket_t> get_socket(const std::string & endpoint) {
+    static std::mutex mutex;
+    std::lock_guard<std::mutex> lock(mutex);
+    static std::unordered_map<std::string, std::weak_ptr<socket_t>> sockets;
+    static bool initialized = false;
+
+    auto it = sockets.find(endpoint);
+    if (it != sockets.end()) {
+        if (auto sock = it->second.lock()) {
+            return sock;
+        }
+    }
+    std::string host;
+    int port;
+    if (!parse_endpoint(endpoint, host, port)) {
+        return nullptr;
+    }
+#ifdef _WIN32
+    if (!initialized) {
+        WSADATA wsaData;
+        int res = WSAStartup(MAKEWORD(2, 2), &wsaData);
+        if (res != 0) {
+            return nullptr;
+        }
+        initialized = true;
+    }
+#else
+    UNUSED(initialized);
+#endif
+    auto sock = socket_connect(host.c_str(), port);
+    if (sock == nullptr) {
+        return nullptr;
+    }
+    GGML_PRINT_DEBUG("[%s] connected to %s, sockfd=%d\n", __func__, endpoint.c_str(), sock->fd);
+    sockets[endpoint] = sock;
+    return sock;
+}
+
+static void ggml_backend_rpc_buffer_free_buffer(ggml_backend_buffer_t buffer) {
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    rpc_msg_free_buffer_req request = {ctx->remote_ptr};
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_FREE_BUFFER, &request, sizeof(request), nullptr, 0);
+    GGML_ASSERT(status);
+    delete ctx;
+}
+
+static void * ggml_backend_rpc_buffer_get_base(ggml_backend_buffer_t buffer) {
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    if (ctx->base_cache.find(buffer) != ctx->base_cache.end()) {
+        return ctx->base_cache[buffer];
+    }
+    rpc_msg_buffer_get_base_req request = {ctx->remote_ptr};
+    rpc_msg_buffer_get_base_rsp response;
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_BUFFER_GET_BASE, &request, sizeof(request), &response, sizeof(response));
+    GGML_ASSERT(status);
+    void * base_ptr = reinterpret_cast<void *>(response.base_ptr);
+    ctx->base_cache[buffer] = base_ptr;
+    return base_ptr;
+}
+
+static rpc_tensor serialize_tensor(const ggml_tensor * tensor) {
+    rpc_tensor result;
+    result.id = reinterpret_cast<uint64_t>(tensor);
+    result.type = tensor->type;
+    if (tensor->buffer) {
+        ggml_backend_buffer_t buffer = tensor->buffer;
+        ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+        result.buffer = ctx->remote_ptr;
+    } else {
+        result.buffer = 0;
+    }
+    for (uint32_t i = 0; i < GGML_MAX_DIMS; i++) {
+        result.ne[i] = tensor->ne[i];
+        result.nb[i] = tensor->nb[i];
+    }
+    result.op = tensor->op;
+    for (uint32_t i = 0; i < GGML_MAX_OP_PARAMS / sizeof(int32_t); i++) {
+        result.op_params[i] = tensor->op_params[i];
+    }
+    result.flags = tensor->flags;
+    for (uint32_t i = 0; i < GGML_MAX_SRC; i++) {
+        result.src[i] = reinterpret_cast<uint64_t>(tensor->src[i]);
+    }
+    result.view_src = reinterpret_cast<uint64_t>(tensor->view_src);
+    result.view_offs = tensor->view_offs;
+    result.data = reinterpret_cast<uint64_t>(tensor->data);
+    snprintf(result.name, GGML_MAX_NAME, "%s", tensor->name);
+    return result;
+}
+
+static void ggml_backend_rpc_buffer_init_tensor(ggml_backend_buffer_t buffer, ggml_tensor * tensor) {
+    UNUSED(buffer);
+    if (ggml_is_quantized(tensor->type)) {
+        // TODO: this check is due to MATRIX_ROW_PADDING in CUDA and should be generalized
+        GGML_ASSERT(tensor->ne[0] % 512 == 0 && "unsupported quantized tensor");
+    }
+}
+
+static void ggml_backend_rpc_buffer_set_tensor(ggml_backend_buffer_t buffer, ggml_tensor * tensor, const void * data, size_t offset, size_t size) {
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    // input serialization format: | rpc_tensor | offset (8 bytes) | data (size bytes) |
+    size_t input_size = sizeof(rpc_tensor) + sizeof(uint64_t) + size;
+    std::vector<uint8_t> input(input_size, 0);
+    rpc_tensor rpc_tensor = serialize_tensor(tensor);
+    memcpy(input.data(), &rpc_tensor, sizeof(rpc_tensor));
+    memcpy(input.data() + sizeof(rpc_tensor), &offset, sizeof(offset));
+    memcpy(input.data() + sizeof(rpc_tensor) + sizeof(offset), data, size);
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_SET_TENSOR, input.data(), input.size(), nullptr, 0);
+    GGML_ASSERT(status);
+}
+
+static void ggml_backend_rpc_buffer_get_tensor(ggml_backend_buffer_t buffer, const ggml_tensor * tensor, void * data, size_t offset, size_t size) {
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    rpc_msg_get_tensor_req request;
+    request.tensor = serialize_tensor(tensor);
+    request.offset = offset;
+    request.size = size;
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_GET_TENSOR, &request, sizeof(request), data, size);
+    GGML_ASSERT(status);
+}
+
+static bool ggml_backend_rpc_buffer_cpy_tensor(ggml_backend_buffer_t buffer, const ggml_tensor * src, ggml_tensor * dst) {
+    // check if src and dst are on the same server
+    ggml_backend_buffer_t src_buffer = src->buffer;
+    ggml_backend_rpc_buffer_context * src_ctx = (ggml_backend_rpc_buffer_context *)src_buffer->context;
+    ggml_backend_buffer_t dst_buffer = dst->buffer;
+    ggml_backend_rpc_buffer_context * dst_ctx = (ggml_backend_rpc_buffer_context *)dst_buffer->context;
+    if (src_ctx->sock != dst_ctx->sock) {
+        return false;
+    }
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    rpc_msg_copy_tensor_req request;
+    request.src = serialize_tensor(src);
+    request.dst = serialize_tensor(dst);
+    rpc_msg_copy_tensor_rsp response;
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_COPY_TENSOR, &request, sizeof(request), &response, sizeof(response));
+    GGML_ASSERT(status);
+    return response.result;
+}
+
+static void ggml_backend_rpc_buffer_clear(ggml_backend_buffer_t buffer, uint8_t value) {
+    ggml_backend_rpc_buffer_context * ctx = (ggml_backend_rpc_buffer_context *)buffer->context;
+    rpc_msg_buffer_clear_req request = {ctx->remote_ptr, value};
+    bool status = send_rpc_cmd(ctx->sock, RPC_CMD_BUFFER_CLEAR, &request, sizeof(request), nullptr, 0);
+    GGML_ASSERT(status);
+}
+
+static ggml_backend_buffer_i ggml_backend_rpc_buffer_interface = {
+    /* .free_buffer     = */ ggml_backend_rpc_buffer_free_buffer,
+    /* .get_base        = */ ggml_backend_rpc_buffer_get_base,
+    /* .init_tensor     = */ ggml_backend_rpc_buffer_init_tensor,
+    /* .memset_tensor   = */ NULL,
+    /* .set_tensor      = */ ggml_backend_rpc_buffer_set_tensor,
+    /* .get_tensor      = */ ggml_backend_rpc_buffer_get_tensor,
+    /* .cpy_tensor      = */ ggml_backend_rpc_buffer_cpy_tensor,
+    /* .clear           = */ ggml_backend_rpc_buffer_clear,
+    /* .reset           = */ NULL,
+};
+
+static const char * ggml_backend_rpc_buffer_type_name(ggml_backend_buffer_type_t buft) {
+    ggml_backend_rpc_buffer_type_context * buft_ctx = (ggml_backend_rpc_buffer_type_context *)buft->context;
+    return buft_ctx->name.c_str();
+}
+
+static ggml_backend_buffer_t ggml_backend_rpc_buffer_type_alloc_buffer(ggml_backend_buffer_type_t buft, size_t size) {
+    ggml_backend_rpc_buffer_type_context * buft_ctx = (ggml_backend_rpc_buffer_type_context *)buft->context;
+    rpc_msg_alloc_buffer_req request = {size};
+    rpc_msg_alloc_buffer_rsp response;
+    auto sock = get_socket(buft_ctx->endpoint);
+    bool status = send_rpc_cmd(sock, RPC_CMD_ALLOC_BUFFER, &request, sizeof(request), &response, sizeof(response));
+    GGML_ASSERT(status);
+    if (response.remote_ptr != 0) {
+        ggml_backend_buffer_t buffer = ggml_backend_buffer_init(buft,
+            ggml_backend_rpc_buffer_interface,
+            new ggml_backend_rpc_buffer_context{sock, {}, response.remote_ptr},
+            response.remote_size);
+        return buffer;
+    } else {
+        return nullptr;
+    }
+}
+
+static size_t get_alignment(const std::shared_ptr<socket_t> & sock) {
+    rpc_msg_get_alignment_rsp response;
+    bool status = send_rpc_cmd(sock, RPC_CMD_GET_ALIGNMENT, nullptr, 0, &response, sizeof(response));
+    GGML_ASSERT(status);
+    return response.alignment;
+}
+
+static size_t ggml_backend_rpc_buffer_type_get_alignment(ggml_backend_buffer_type_t buft) {
+    ggml_backend_rpc_buffer_type_context * buft_ctx = (ggml_backend_rpc_buffer_type_context *)buft->context;
+    return buft_ctx->alignment;
+}
+
+static size_t get_max_size(const std::shared_ptr<socket_t> & sock) {
+    rpc_msg_get_max_size_rsp response;
+    bool status = send_rpc_cmd(sock, RPC_CMD_GET_MAX_SIZE, nullptr, 0, &response, sizeof(response));
+    GGML_ASSERT(status);
+    return response.max_size;
+}
+
+static size_t ggml_backend_rpc_get_max_size(ggml_backend_buffer_type_t buft) {
+    ggml_backend_rpc_buffer_type_context * buft_ctx = (ggml_backend_rpc_buffer_type_context *)buft->context;
+    return buft_ctx->max_size;
+}
+
+static size_t ggml_backend_rpc_buffer_type_get_alloc_size(ggml_backend_buffer_type_t buft, const ggml_tensor * tensor) {
+    UNUSED(buft);
+    return ggml_nbytes(tensor);
+}
+
+static ggml_backend_buffer_type_i ggml_backend_rpc_buffer_type_interface = {
+    /* .get_name         = */ ggml_backend_rpc_buffer_type_name,
+    /* .alloc_buffer     = */ ggml_backend_rpc_buffer_type_alloc_buffer,
+    /* .get_alignment    = */ ggml_backend_rpc_buffer_type_get_alignment,
+    /* .get_max_size     = */ ggml_backend_rpc_get_max_size,
+    /* .get_alloc_size   = */ ggml_backend_rpc_buffer_type_get_alloc_size,
+    /* .is_host          = */ NULL,
+};
+
+static const char * ggml_backend_rpc_name(ggml_backend_t backend) {
+    ggml_backend_rpc_context * rpc_ctx = (ggml_backend_rpc_context *)backend->context;
+
+    return rpc_ctx->name.c_str();
+}
+
+static void ggml_backend_rpc_free(ggml_backend_t backend) {
+    ggml_backend_rpc_context * rpc_ctx = (ggml_backend_rpc_context *)backend->context;
+    delete rpc_ctx;
+    delete backend;
+}
+
+static void ggml_backend_rpc_synchronize(ggml_backend_t backend) {
+    UNUSED(backend);
+    // this is no-op because we don't have any async operations
+}
+
+static void add_tensor(ggml_tensor * tensor, std::vector<rpc_tensor> & tensors, std::unordered_set<ggml_tensor*> & visited) {
+    if (tensor == nullptr) {
+        return;
+    }
+    if (visited.find(tensor) != visited.end()) {
+        return;
+    }
+    visited.insert(tensor);
+    for (int i = 0; i < GGML_MAX_SRC; i++) {
+        add_tensor(tensor->src[i], tensors, visited);
+    }
+    add_tensor(tensor->view_src, tensors, visited);
+    tensors.push_back(serialize_tensor(tensor));
+}
+
+static void serialize_graph(const ggml_cgraph * cgraph, std::vector<uint8_t> & output) {
+    uint32_t n_nodes = cgraph->n_nodes;
+    std::vector<rpc_tensor> tensors;
+    std::unordered_set<ggml_tensor*> visited;
+    for (uint32_t i = 0; i < n_nodes; i++) {
+        add_tensor(cgraph->nodes[i], tensors, visited);
+    }
+    // serialization format:
+    // | n_nodes (4 bytes) | nodes (n_nodes * sizeof(uint64_t) | n_tensors (4 bytes) | tensors (n_tensors * sizeof(rpc_tensor)) |
+    uint32_t n_tensors = tensors.size();
+    int output_size = sizeof(uint32_t) + n_nodes * sizeof(uint64_t) + sizeof(uint32_t) + n_tensors * sizeof(rpc_tensor);
+    output.resize(output_size, 0);
+    memcpy(output.data(), &n_nodes, sizeof(n_nodes));
+    for (uint32_t i = 0; i < n_nodes; i++) {
+        memcpy(output.data() + sizeof(n_nodes) + i * sizeof(uint64_t), &cgraph->nodes[i], sizeof(uint64_t));
+    }
+    uint32_t * out_ntensors = (uint32_t *)(output.data() + sizeof(n_nodes) + n_nodes * sizeof(uint64_t));
+    *out_ntensors = n_tensors;
+    rpc_tensor * out_tensors = (rpc_tensor *)(output.data() + sizeof(n_nodes) + n_nodes * sizeof(uint64_t) + sizeof(uint32_t));
+    memcpy(out_tensors, tensors.data(), n_tensors * sizeof(rpc_tensor));
+}
+
+static enum ggml_status ggml_backend_rpc_graph_compute(ggml_backend_t backend, ggml_cgraph * cgraph) {
+    ggml_backend_rpc_context * rpc_ctx = (ggml_backend_rpc_context *)backend->context;
+    std::vector<uint8_t> input;
+    serialize_graph(cgraph, input);
+    rpc_msg_graph_compute_rsp response;
+    auto sock = get_socket(rpc_ctx->endpoint);
+    bool status = send_rpc_cmd(sock, RPC_CMD_GRAPH_COMPUTE, input.data(), input.size(), &response, sizeof(response));
+    GGML_ASSERT(status);
+    return (enum ggml_status)response.result;
+}
+
+static ggml_backend_i ggml_backend_rpc_interface = {
+    /* .get_name                = */ ggml_backend_rpc_name,
+    /* .free                    = */ ggml_backend_rpc_free,
+    /* .set_tensor_async        = */ NULL,
+    /* .get_tensor_async        = */ NULL,
+    /* .cpy_tensor_async        = */ NULL,
+    /* .synchronize             = */ ggml_backend_rpc_synchronize,
+    /* .graph_plan_create       = */ NULL,
+    /* .graph_plan_free         = */ NULL,
+    /* .graph_plan_update       = */ NULL,
+    /* .graph_plan_compute      = */ NULL,
+    /* .graph_compute           = */ ggml_backend_rpc_graph_compute,
+    /* .event_record            = */ NULL,
+    /* .event_wait              = */ NULL,
+};
+
+GGML_API ggml_backend_buffer_type_t ggml_backend_rpc_buffer_type(const char * endpoint) {
+    static std::mutex mutex;
+    std::lock_guard<std::mutex> lock(mutex);
+    // NOTE: buffer types are allocated and never freed; this is by design
+    static std::unordered_map<std::string, ggml_backend_buffer_type_t> buft_map;
+    auto it = buft_map.find(endpoint);
+    if (it != buft_map.end()) {
+        return it->second;
+    }
+    auto sock = get_socket(endpoint);
+    if (sock == nullptr) {
+        fprintf(stderr, "Failed to connect to %s\n", endpoint);
+        return nullptr;
+    }
+    size_t alignment = get_alignment(sock);
+    size_t max_size = get_max_size(sock);
+    ggml_backend_rpc_buffer_type_context * buft_ctx = new ggml_backend_rpc_buffer_type_context {
+        /* .endpoint  = */ endpoint,
+        /* .name      = */ "RPC[" + std::string(endpoint) + "]",
+        /* .alignment = */ alignment,
+        /* .max_size  = */ max_size
+    };
+
+    ggml_backend_buffer_type_t buft = new ggml_backend_buffer_type {
+        /* .iface   = */ ggml_backend_rpc_buffer_type_interface,
+        /* .device  = */ ggml_backend_rpc_add_device(endpoint),
+        /* .context = */ buft_ctx
+    };
+    buft_map[endpoint] = buft;
+    return buft;
+}
+
+ggml_backend_t ggml_backend_rpc_init(const char * endpoint) {
+    ggml_backend_rpc_context * ctx = new ggml_backend_rpc_context {
+        /* .endpoint  = */ endpoint,
+        /* .name      = */ "RPC[" + std::string(endpoint) + "]",
+    };
+
+    ggml_backend_t backend = new ggml_backend {
+        /* .guid      = */ ggml_backend_rpc_guid(),
+        /* .interface = */ ggml_backend_rpc_interface,
+        /* .device    = */ ggml_backend_rpc_add_device(endpoint),
+        /* .context   = */ ctx
+    };
+    return backend;
+}
+
+GGML_API bool ggml_backend_is_rpc(ggml_backend_t backend) {
+    return backend != NULL && ggml_guid_matches(backend->guid, ggml_backend_rpc_guid());
+}
+
+static void get_device_memory(const std::shared_ptr<socket_t> & sock, size_t * free, size_t * total) {
+    rpc_msg_get_device_memory_rsp response;
+    bool status = send_rpc_cmd(sock, RPC_CMD_GET_DEVICE_MEMORY, nullptr, 0, &response, sizeof(response));
+    GGML_ASSERT(status);
+    *free = response.free_mem;
+    *total = response.total_mem;
+}
+
+GGML_API void ggml_backend_rpc_get_device_memory(const char * endpoint, size_t * free, size_t * total) {
+    auto sock = get_socket(endpoint);
+    if (sock == nullptr) {
+        *free = 0;
+        *total = 0;
+        return;
+    }
+    get_device_memory(sock, free, total);
+}
+
+// RPC server-side implementation
+
+class rpc_server {
+public:
+    rpc_server(ggml_backend_t backend) : backend(backend) {}
+    ~rpc_server();
+
+    void alloc_buffer(const rpc_msg_alloc_buffer_req & request, rpc_msg_alloc_buffer_rsp & response);
+    void get_alignment(rpc_msg_get_alignment_rsp & response);
+    void get_max_size(rpc_msg_get_max_size_rsp & response);
+    bool buffer_get_base(const rpc_msg_buffer_get_base_req & request, rpc_msg_buffer_get_base_rsp & response);
+    bool free_buffer(const rpc_msg_free_buffer_req & request);
+    bool buffer_clear(const rpc_msg_buffer_clear_req & request);
+    bool set_tensor(const std::vector<uint8_t> & input);
+    bool get_tensor(const rpc_msg_get_tensor_req & request, std::vector<uint8_t> & response);
+    bool copy_tensor(const rpc_msg_copy_tensor_req & request, rpc_msg_copy_tensor_rsp & response);
+    bool graph_compute(const std::vector<uint8_t> & input, rpc_msg_graph_compute_rsp & response);
+
+private:
+    ggml_tensor * deserialize_tensor(struct ggml_context * ctx, const rpc_tensor * tensor);
+    ggml_tensor * create_node(uint64_t id,
+                              struct ggml_context * ctx,
+                              const std::unordered_map<uint64_t, const rpc_tensor*> & tensor_ptrs,
+                              std::unordered_map<uint64_t, struct ggml_tensor*> & tensor_map);
+
+
+    ggml_backend_t backend;
+    std::unordered_set<ggml_backend_buffer_t> buffers;
+};
+
+void rpc_server::alloc_buffer(const rpc_msg_alloc_buffer_req & request, rpc_msg_alloc_buffer_rsp & response) {
+    ggml_backend_buffer_type_t buft = ggml_backend_get_default_buffer_type(backend);
+    ggml_backend_buffer_t buffer = ggml_backend_buft_alloc_buffer(buft, request.size);
+    response.remote_ptr = 0;
+    response.remote_size = 0;
+    if (buffer != nullptr) {
+        response.remote_ptr = reinterpret_cast<uint64_t>(buffer);
+        response.remote_size = buffer->size;
+        GGML_PRINT_DEBUG("[%s] size: %" PRIu64 " -> remote_ptr: %" PRIx64 ", remote_size: %" PRIu64 "\n", __func__, request.size, response.remote_ptr, response.remote_size);
+        buffers.insert(buffer);
+    } else {
+        GGML_PRINT_DEBUG("[%s] size: %" PRIu64 " -> failed\n", __func__, request.size);
+    }
+}
+
+void rpc_server::get_alignment(rpc_msg_get_alignment_rsp & response) {
+    ggml_backend_buffer_type_t buft = ggml_backend_get_default_buffer_type(backend);
+    size_t alignment = ggml_backend_buft_get_alignment(buft);
+    GGML_PRINT_DEBUG("[%s] alignment: %lu\n", __func__, alignment);
+    response.alignment = alignment;
+}
+
+void rpc_server::get_max_size(rpc_msg_get_max_size_rsp & response) {
+    ggml_backend_buffer_type_t buft = ggml_backend_get_default_buffer_type(backend);
+    size_t max_size = ggml_backend_buft_get_max_size(buft);
+    GGML_PRINT_DEBUG("[%s] max_size: %lu\n", __func__, max_size);
+    response.max_size = max_size;
+}
+
+bool rpc_server::buffer_get_base(const rpc_msg_buffer_get_base_req & request, rpc_msg_buffer_get_base_rsp & response) {
+    GGML_PRINT_DEBUG("[%s] remote_ptr: %" PRIx64 "\n", __func__, request.remote_ptr);
+    ggml_backend_buffer_t buffer = reinterpret_cast<ggml_backend_buffer_t>(request.remote_ptr);
+    if (buffers.find(buffer) == buffers.end()) {
+        GGML_PRINT_DEBUG("[%s] buffer not found\n", __func__);
+        return false;
+    }
+    void * base = ggml_backend_buffer_get_base(buffer);
+    response.base_ptr = reinterpret_cast<uint64_t>(base);
+    return true;
+}
+
+bool rpc_server::free_buffer(const rpc_msg_free_buffer_req & request) {
+    GGML_PRINT_DEBUG("[%s] remote_ptr: %" PRIx64 "\n", __func__, request.remote_ptr);
+    ggml_backend_buffer_t buffer = reinterpret_cast<ggml_backend_buffer_t>(request.remote_ptr);
+    if (buffers.find(buffer) == buffers.end()) {
+        GGML_PRINT_DEBUG("[%s] buffer not found\n", __func__);
+        return false;
+    }
+    ggml_backend_buffer_free(buffer);
+    buffers.erase(buffer);
+    return true;
+}
+
+bool rpc_server::buffer_clear(const rpc_msg_buffer_clear_req & request) {
+    GGML_PRINT_DEBUG("[%s] remote_ptr: %" PRIx64 ", value: %u\n", __func__, request.remote_ptr, request.value);
+    ggml_backend_buffer_t buffer = reinterpret_cast<ggml_backend_buffer_t>(request.remote_ptr);
+    if (buffers.find(buffer) == buffers.end()) {
+        GGML_PRINT_DEBUG("[%s] buffer not found\n", __func__);
+        return false;
+    }
+    ggml_backend_buffer_clear(buffer, request.value);
+    return true;
+}
+
+ggml_tensor * rpc_server::deserialize_tensor(struct ggml_context * ctx, const rpc_tensor * tensor) {
+    ggml_tensor * result = ggml_new_tensor_4d(ctx, (ggml_type) tensor->type,
+        tensor->ne[0], tensor->ne[1], tensor->ne[2], tensor->ne[3]);
+    for (uint32_t i = 0; i < GGML_MAX_DIMS; i++) {
+        result->nb[i] = tensor->nb[i];
+    }
+    result->buffer = reinterpret_cast<ggml_backend_buffer_t>(tensor->buffer);
+    if (result->buffer && buffers.find(result->buffer) == buffers.end()) {
+        result->buffer = nullptr;
+    }
+
+    if (result->buffer) {
+        // require that the tensor data does not go beyond the buffer end
+        uint64_t tensor_size = (uint64_t) ggml_nbytes(result);
+        uint64_t buffer_start = (uint64_t) ggml_backend_buffer_get_base(result->buffer);
+        uint64_t buffer_size = (uint64_t) ggml_backend_buffer_get_size(result->buffer);
+        GGML_ASSERT(tensor->data + tensor_size >= tensor->data); // check for overflow
+        GGML_ASSERT(tensor->data >= buffer_start && tensor->data + tensor_size <= buffer_start + buffer_size);
+    }
+
+    result->op = (ggml_op) tensor->op;
+    for (uint32_t i = 0; i < GGML_MAX_OP_PARAMS / sizeof(int32_t); i++) {
+        result->op_params[i] = tensor->op_params[i];
+    }
+    result->flags = tensor->flags;
+    result->data = reinterpret_cast<void *>(tensor->data);
+    ggml_set_name(result, tensor->name);
+    return result;
+}
+
+
+bool rpc_server::set_tensor(const std::vector<uint8_t> & input) {
+    // serialization format: | rpc_tensor | offset (8 bytes) | data (size bytes) |
+    if (input.size() < sizeof(rpc_tensor) + sizeof(uint64_t)) {
+        return false;
+    }
+    const rpc_tensor * in_tensor = (const rpc_tensor *)input.data();
+    uint64_t offset;
+    memcpy(&offset, input.data() + sizeof(rpc_tensor), sizeof(offset));
+    const size_t size = input.size() - sizeof(rpc_tensor) - sizeof(offset);
+
+    struct ggml_init_params params {
+        /*.mem_size   =*/ ggml_tensor_overhead(),
+        /*.mem_buffer =*/ NULL,
+        /*.no_alloc   =*/ true,
+    };
+    struct ggml_context * ctx = ggml_init(params);
+    ggml_tensor * tensor = deserialize_tensor(ctx, in_tensor);
+    if (tensor == nullptr) {
+        GGML_PRINT_DEBUG("[%s] error deserializing tensor\n", __func__);
+        ggml_free(ctx);
+        return false;
+    }
+    GGML_PRINT_DEBUG("[%s] buffer: %p, data: %p, offset: %" PRIu64 ", size: %zu\n", __func__, (void*)tensor->buffer, tensor->data, offset, size);
+
+    // sanitize tensor->data
+    {
+        const size_t p0 = (size_t) ggml_backend_buffer_get_base(tensor->buffer);
+        const size_t p1 = p0 + ggml_backend_buffer_get_size(tensor->buffer);
+
+        if (in_tensor->data + offset < p0 || in_tensor->data + offset >= p1 || size > (p1 - in_tensor->data - offset)) {
+            GGML_ABORT("[%s] tensor->data out of bounds\n", __func__);
+        }
+    }
+
+    const void * data = input.data() + sizeof(rpc_tensor) + sizeof(offset);
+    ggml_backend_tensor_set(tensor, data, offset, size);
+    ggml_free(ctx);
+    return true;
+}
+
+bool rpc_server::get_tensor(const rpc_msg_get_tensor_req & request, std::vector<uint8_t> & response) {
+    struct ggml_init_params params {
+        /*.mem_size   =*/ ggml_tensor_overhead(),
+        /*.mem_buffer =*/ NULL,
+        /*.no_alloc   =*/ true,
+    };
+    struct ggml_context * ctx = ggml_init(params);
+    ggml_tensor * tensor = deserialize_tensor(ctx, &request.tensor);
+    if (tensor == nullptr) {
+        GGML_PRINT_DEBUG("[%s] error deserializing tensor\n", __func__);
+        ggml_free(ctx);
+        return false;
+    }
+    GGML_PRINT_DEBUG("[%s] buffer: %p, data: %p, offset: %" PRIu64 ", size: %" PRIu64 "\n", __func__, (void*)tensor->buffer, tensor->data, request.offset, request.size);
+
+    // sanitize tensor->data
+    {
+        const size_t p0 = (size_t) ggml_backend_buffer_get_base(tensor->buffer);
+        const size_t p1 = p0 + ggml_backend_buffer_get_size(tensor->buffer);
+
+        if (request.tensor.data + request.offset < p0 ||
+            request.tensor.data + request.offset >= p1 ||
+            request.size > (p1 - request.tensor.data - request.offset)) {
+                GGML_ABORT("[%s] tensor->data out of bounds\n", __func__);
+        }
+    }
+
+    response.resize(request.size, 0);
+    ggml_backend_tensor_get(tensor, response.data(), request.offset, request.size);
+    ggml_free(ctx);
+    return true;
+}
+
+bool rpc_server::copy_tensor(const rpc_msg_copy_tensor_req & request, rpc_msg_copy_tensor_rsp & response) {
+    struct ggml_init_params params {
+        /*.mem_size   =*/ 2*ggml_tensor_overhead(),
+        /*.mem_buffer =*/ NULL,
+        /*.no_alloc   =*/ true,
+    };
+    struct ggml_context * ctx = ggml_init(params);
+    ggml_tensor * src = deserialize_tensor(ctx, &request.src);
+    ggml_tensor * dst = deserialize_tensor(ctx, &request.dst);
+    if (src == nullptr || dst == nullptr) {
+        GGML_PRINT_DEBUG("[%s] error deserializing tensors\n", __func__);
+        ggml_free(ctx);
+        return false;
+    }
+    GGML_PRINT_DEBUG("[%s] src->buffer: %p, dst->buffer: %p\n", __func__, (void*)src->buffer, (void*)dst->buffer);
+    response.result = ggml_backend_buffer_copy_tensor(src, dst);
+    ggml_free(ctx);
+    return true;
+}
+
+ggml_tensor * rpc_server::create_node(uint64_t id,
+                                      struct ggml_context * ctx,
+                                      const std::unordered_map<uint64_t, const rpc_tensor*> & tensor_ptrs,
+                                      std::unordered_map<uint64_t, struct ggml_tensor*> & tensor_map) {
+    if (id == 0) {
+        return nullptr;
+    }
+    if (tensor_map.find(id) != tensor_map.end()) {
+        return tensor_map[id];
+    }
+    const rpc_tensor * tensor = tensor_ptrs.at(id);
+    struct ggml_tensor * result = deserialize_tensor(ctx, tensor);
+    if (result == nullptr) {
+        return nullptr;
+    }
+    tensor_map[id] = result;
+    for (int i = 0; i < GGML_MAX_SRC; i++) {
+        result->src[i] = create_node(tensor->src[i], ctx, tensor_ptrs, tensor_map);
+    }
+    result->view_src = create_node(tensor->view_src, ctx, tensor_ptrs, tensor_map);
+    result->view_offs = tensor->view_offs;
+    return result;
+}
+
+bool rpc_server::graph_compute(const std::vector<uint8_t> & input, rpc_msg_graph_compute_rsp & response) {
+    // serialization format:
+    // | n_nodes (4 bytes) | nodes (n_nodes * sizeof(uint64_t) | n_tensors (4 bytes) | tensors (n_tensors * sizeof(rpc_tensor)) |
+    if (input.size() < sizeof(uint32_t)) {
+        return false;
+    }
+    uint32_t n_nodes;
+    memcpy(&n_nodes, input.data(), sizeof(n_nodes));
+    if (input.size() < sizeof(uint32_t) + n_nodes*sizeof(uint64_t) + sizeof(uint32_t)) {
+        return false;
+    }
+    const uint64_t * nodes = (const uint64_t *)(input.data() + sizeof(n_nodes));
+    uint32_t n_tensors;
+    memcpy(&n_tensors, input.data() + sizeof(n_nodes) + n_nodes*sizeof(uint64_t), sizeof(n_tensors));
+    if (input.size() < sizeof(uint32_t) + n_nodes*sizeof(uint64_t) + sizeof(uint32_t) + n_tensors*sizeof(rpc_tensor)) {
+        return false;
+    }
+    const rpc_tensor * tensors = (const rpc_tensor *)(input.data() + sizeof(n_nodes) + n_nodes*sizeof(uint64_t) + sizeof(n_tensors));
+    GGML_PRINT_DEBUG("[%s] n_nodes: %u, n_tensors: %u\n", __func__, n_nodes, n_tensors);
+
+    size_t buf_size = ggml_tensor_overhead()*(n_nodes + n_tensors) + ggml_graph_overhead_custom(n_nodes, false);
+    struct ggml_init_params params = {
+        /*.mem_size   =*/ buf_size,
+        /*.mem_buffer =*/ NULL,
+        /*.no_alloc   =*/ true,
+    };
+    struct ggml_context * ctx = ggml_init(params);
+    struct ggml_cgraph * graph = ggml_new_graph_custom(ctx, n_nodes, false);
+    graph->n_nodes = n_nodes;
+    std::unordered_map<uint64_t, const rpc_tensor*> tensor_ptrs;
+    for (uint32_t i = 0; i < n_tensors; i++) {
+        tensor_ptrs[tensors[i].id] = &tensors[i];
+    }
+    std::unordered_map<uint64_t, ggml_tensor*> tensor_map;
+    for (uint32_t i = 0; i < n_nodes; i++) {
+        int64_t id;
+        memcpy(&id, &nodes[i], sizeof(id));
+        graph->nodes[i] = create_node(id, ctx, tensor_ptrs, tensor_map);
+    }
+    ggml_status status = ggml_backend_graph_compute(backend, graph);
+    response.result = status;
+    ggml_free(ctx);
+    return true;
+}
+
+rpc_server::~rpc_server() {
+    for (auto buffer : buffers) {
+        ggml_backend_buffer_free(buffer);
+    }
+}
+
+static void rpc_serve_client(ggml_backend_t backend, sockfd_t sockfd, size_t free_mem, size_t total_mem) {
+    rpc_server server(backend);
+    while (true) {
+        uint8_t cmd;
+        if (!recv_data(sockfd, &cmd, 1)) {
+            break;
+        }
+        if (cmd >= RPC_CMD_COUNT) {
+            // fail fast if the command is invalid
+            fprintf(stderr, "Unknown command: %d\n", cmd);
+            break;
+        }
+        switch (cmd) {
+            case RPC_CMD_ALLOC_BUFFER: {
+                rpc_msg_alloc_buffer_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                rpc_msg_alloc_buffer_rsp response;
+                server.alloc_buffer(request, response);
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_GET_ALIGNMENT: {
+                if (!recv_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                rpc_msg_get_alignment_rsp response;
+                server.get_alignment(response);
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_GET_MAX_SIZE: {
+                if (!recv_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                rpc_msg_get_max_size_rsp response;
+                server.get_max_size(response);
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_BUFFER_GET_BASE: {
+                rpc_msg_buffer_get_base_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                rpc_msg_buffer_get_base_rsp response;
+                if (!server.buffer_get_base(request, response)) {
+                    return;
+                }
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_FREE_BUFFER: {
+                rpc_msg_free_buffer_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                if (!server.free_buffer(request)) {
+                    return;
+                }
+                if (!send_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_BUFFER_CLEAR: {
+                rpc_msg_buffer_clear_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                if (!server.buffer_clear(request)) {
+                    return;
+                }
+                if (!send_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_SET_TENSOR: {
+                std::vector<uint8_t> input;
+                if (!recv_msg(sockfd, input)) {
+                    return;
+                }
+                if (!server.set_tensor(input)) {
+                    return;
+                }
+                if (!send_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_GET_TENSOR: {
+                rpc_msg_get_tensor_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                std::vector<uint8_t> response;
+                if (!server.get_tensor(request, response)) {
+                    return;
+                }
+                if (!send_msg(sockfd, response.data(), response.size())) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_COPY_TENSOR: {
+                rpc_msg_copy_tensor_req request;
+                if (!recv_msg(sockfd, &request, sizeof(request))) {
+                    return;
+                }
+                rpc_msg_copy_tensor_rsp response;
+                if (!server.copy_tensor(request, response)) {
+                    return;
+                }
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_GRAPH_COMPUTE: {
+                std::vector<uint8_t> input;
+                if (!recv_msg(sockfd, input)) {
+                    return;
+                }
+                rpc_msg_graph_compute_rsp response;
+                if (!server.graph_compute(input, response)) {
+                    return;
+                }
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            case RPC_CMD_GET_DEVICE_MEMORY: {
+                if (!recv_msg(sockfd, nullptr, 0)) {
+                    return;
+                }
+                rpc_msg_get_device_memory_rsp response;
+                response.free_mem = free_mem;
+                response.total_mem = total_mem;
+                if (!send_msg(sockfd, &response, sizeof(response))) {
+                    return;
+                }
+                break;
+            }
+            default: {
+                fprintf(stderr, "Unknown command: %d\n", cmd);
+                return;
+            }
+        }
+    }
+}
+
+void ggml_backend_rpc_start_server(ggml_backend_t backend, const char * endpoint, size_t free_mem, size_t total_mem) {
+    std::string host;
+    int port;
+    if (!parse_endpoint(endpoint, host, port)) {
+        return;
+    }
+#ifdef _WIN32
+    {
+        WSADATA wsaData;
+        int res = WSAStartup(MAKEWORD(2, 2), &wsaData);
+        if (res != 0) {
+            fprintf(stderr, "WSAStartup failed: %d\n", res);
+            return;
+        }
+    }
+#endif
+    auto server_socket = create_server_socket(host.c_str(), port);
+    if (server_socket == nullptr) {
+        fprintf(stderr, "Failed to create server socket\n");
+        return;
+    }
+    while (true) {
+        auto client_socket = socket_accept(server_socket->fd);
+        if (client_socket == nullptr) {
+            fprintf(stderr, "Failed to accept client connection\n");
+            return;
+        }
+        printf("Accepted client connection, free_mem=%zu, total_mem=%zu\n", free_mem, total_mem);
+        fflush(stdout);
+        rpc_serve_client(backend, client_socket->fd, free_mem, total_mem);
+        printf("Client connection closed\n");
+        fflush(stdout);
+    }
+#ifdef _WIN32
+    WSACleanup();
+#endif
+}
+
+// device interface
+
+struct ggml_backend_rpc_device_context {
+    std::string endpoint;
+    std::string name;
+};
+
+static const char * ggml_backend_rpc_device_get_name(ggml_backend_dev_t dev) {
+    ggml_backend_rpc_device_context * ctx = (ggml_backend_rpc_device_context *)dev->context;
+
+    return ctx->name.c_str();
+}
+
+static const char * ggml_backend_rpc_device_get_description(ggml_backend_dev_t dev) {
+    ggml_backend_rpc_device_context * ctx = (ggml_backend_rpc_device_context *)dev->context;
+
+    return ctx->name.c_str();
+}
+
+static void ggml_backend_rpc_device_get_memory(ggml_backend_dev_t dev, size_t * free, size_t * total) {
+    ggml_backend_rpc_device_context * ctx = (ggml_backend_rpc_device_context *)dev->context;
+
+    ggml_backend_rpc_get_device_memory(ctx->endpoint.c_str(), free, total);
+
+    UNUSED(dev);
+}
+
+static enum ggml_backend_dev_type ggml_backend_rpc_device_get_type(ggml_backend_dev_t dev) {
+    // TODO: obtain value from the server
+    return GGML_BACKEND_DEVICE_TYPE_GPU;
+
+    UNUSED(dev);
+}
+
+static void ggml_backend_rpc_device_get_props(ggml_backend_dev_t dev, struct ggml_backend_dev_props * props) {
+    props->name        = ggml_backend_rpc_device_get_name(dev);
+    props->description = ggml_backend_rpc_device_get_description(dev);
+    props->type        = ggml_backend_rpc_device_get_type(dev);
+    ggml_backend_rpc_device_get_memory(dev, &props->memory_free, &props->memory_total);
+    props->caps = {
+        /* .async                 = */ false,
+        /* .host_buffer           = */ false,
+        /* .buffer_from_host_ptr  = */ false,
+        /* .events                = */ false,
+    };
+}
+
+static ggml_backend_t ggml_backend_rpc_device_init(ggml_backend_dev_t dev, const char * params) {
+    ggml_backend_rpc_device_context * ctx = (ggml_backend_rpc_device_context *)dev->context;
+
+    return ggml_backend_rpc_init(ctx->endpoint.c_str());
+
+    UNUSED(params);
+}
+
+static ggml_backend_buffer_type_t ggml_backend_rpc_device_get_buffer_type(ggml_backend_dev_t dev) {
+    ggml_backend_rpc_device_context * ctx = (ggml_backend_rpc_device_context *)dev->context;
+
+    return ggml_backend_rpc_buffer_type(ctx->endpoint.c_str());
+
+    UNUSED(dev);
+}
+
+static bool ggml_backend_rpc_device_supports_op(ggml_backend_dev_t dev, const struct ggml_tensor * op) {
+    UNUSED(dev);
+    UNUSED(op);
+    //TODO: call the remote backend and cache the results
+    return true;
+}
+
+static bool ggml_backend_rpc_device_supports_buft(ggml_backend_dev_t dev, ggml_backend_buffer_type_t buft) {
+    if (!buft || buft->iface.get_name != ggml_backend_rpc_buffer_type_name) {
+        return false;
+    }
+    ggml_backend_rpc_buffer_type_context * buft_ctx = (ggml_backend_rpc_buffer_type_context *)buft->context;
+    ggml_backend_rpc_device_context * dev_ctx = (ggml_backend_rpc_device_context *)dev->context;
+    return buft_ctx->endpoint == dev_ctx->endpoint;
+}
+
+static const struct ggml_backend_device_i ggml_backend_rpc_device_i = {
+    /* .get_name             = */ ggml_backend_rpc_device_get_name,
+    /* .get_description      = */ ggml_backend_rpc_device_get_description,
+    /* .get_memory           = */ ggml_backend_rpc_device_get_memory,
+    /* .get_type             = */ ggml_backend_rpc_device_get_type,
+    /* .get_props            = */ ggml_backend_rpc_device_get_props,
+    /* .init_backend         = */ ggml_backend_rpc_device_init,
+    /* .get_buffer_type      = */ ggml_backend_rpc_device_get_buffer_type,
+    /* .get_host_buffer_type = */ NULL,
+    /* .buffer_from_host_ptr = */ NULL,
+    /* .supports_op          = */ ggml_backend_rpc_device_supports_op,
+    /* .supports_buft        = */ ggml_backend_rpc_device_supports_buft,
+    /* .offload_op           = */ NULL,
+    /* .event_new            = */ NULL,
+    /* .event_free           = */ NULL,
+    /* .event_synchronize    = */ NULL,
+};
+
+// backend reg interface
+
+static const char * ggml_backend_rpc_reg_get_name(ggml_backend_reg_t reg) {
+    return "RPC";
+
+    UNUSED(reg);
+}
+
+static size_t ggml_backend_rpc_reg_get_device_count(ggml_backend_reg_t reg) {
+    return 0;
+
+    UNUSED(reg);
+}
+
+static ggml_backend_dev_t ggml_backend_rpc_reg_get_device(ggml_backend_reg_t reg, size_t index) {
+    GGML_ABORT("The RPC backend does not have enumerated devices - use ggml_backend_add_device instead");
+
+    UNUSED(reg);
+    UNUSED(index);
+}
+
+static void * ggml_backend_rpc_get_proc_address(ggml_backend_reg_t reg, const char * name) {
+    if (std::strcmp(name, "ggml_backend_rpc_add_device") == 0) {
+        return (void *)ggml_backend_rpc_add_device;
+    }
+    return NULL;
+
+    UNUSED(reg);
+}
+
+static const struct ggml_backend_reg_i ggml_backend_rpc_reg_i = {
+    /* .get_name         = */ ggml_backend_rpc_reg_get_name,
+    /* .get_device_count = */ ggml_backend_rpc_reg_get_device_count,
+    /* .get_device       = */ ggml_backend_rpc_reg_get_device,
+    /* .get_proc_address = */ ggml_backend_rpc_get_proc_address,
+};
+
+ggml_backend_reg_t ggml_backend_rpc_reg(void) {
+    static struct ggml_backend_reg ggml_backend_rpc_reg = {
+        /* .iface   = */ ggml_backend_rpc_reg_i,
+        /* .context = */ NULL,
+    };
+
+    return &ggml_backend_rpc_reg;
+}
+
+ggml_backend_dev_t ggml_backend_rpc_add_device(const char * endpoint) {
+    static std::unordered_map<std::string, ggml_backend_dev_t> dev_map;
+
+    static std::mutex mutex;
+    std::lock_guard<std::mutex> lock(mutex);
+
+    if (dev_map.find(endpoint) != dev_map.end()) {
+        return dev_map[endpoint];
+    }
+
+    ggml_backend_rpc_device_context * ctx = new ggml_backend_rpc_device_context {
+        /* .endpoint = */ endpoint,
+        /* .name     = */ "RPC[" + std::string(endpoint) + "]",
+    };
+
+    ggml_backend_dev_t dev = new ggml_backend_device {
+        /* .iface   = */ ggml_backend_rpc_device_i,
+        /* .reg     = */ ggml_backend_rpc_reg(),
+        /* .context = */ ctx,
+    };
+
+    dev_map[endpoint] = dev;
+
+    return dev;
+}