jsonrpc-fdpass-go

A Go implementation of JSON-RPC 2.0 with file descriptor passing over Unix domain sockets.

This library implements the protocol specified in jsonrpc-fdpass.

Protocol Overview

• Transport: Unix domain sockets (SOCK_STREAM)
• Framing: Self-delimiting JSON (streaming parser)
• FD Passing: Via sendmsg/recvmsg with SCM_RIGHTS ancillary data
• FD Count: Top-level fds field indicates the number of file descriptors attached

When file descriptors are attached to a message, the fds field is automatically set to the count of FDs. File descriptors are passed positionally—the application layer defines the semantic mapping between FD positions and parameters.

Installation

go get github.com/cgwalters/jsonrpc-fdpass-go

Usage

package main

import (
    "net"
    "os"

    fdpass "github.com/cgwalters/jsonrpc-fdpass-go"
)

func main() {
    // Connect to a Unix socket
    conn, _ := net.DialUnix("unix", nil, &net.UnixAddr{Name: "/tmp/socket.sock", Net: "unix"})

    // Create sender and receiver
    sender := fdpass.NewSender(conn)
    receiver := fdpass.NewReceiver(conn)

    // Send a request with a file descriptor
    file, _ := os.Open("example.txt")
    defer file.Close()

    req := fdpass.NewRequest("readFile", map[string]interface{}{
        "path": "example.txt",
    }, 1)

    msg := &fdpass.MessageWithFds{
        Message:         req,
        FileDescriptors: []*os.File{file},
    }

    // The sender automatically sets the "fds" field to 1
    sender.Send(msg)

    // Receive response
    resp, _ := receiver.Receive()
    // Handle resp.Message and resp.FileDescriptors
}

License

MIT