STUN Client Go

An implementation written by @jameshi16.

This is a partial implementation of the RFC 5389, albiet not fully. The implemented attributes are:

• MAPPED-ADDRESS
• XOR-MAPPED-ADDRESS

I'm too lazy to implement the rest of the attributes, because they weren't critical to my usage. This may get a full implementation in the future.

Why

For UDP Hole Punching, which is a form of NAT Traversal. Useful for P2P connections.

How to use

The package that contains the STUN Agent only has one exported function, which is stun_c.RequestRemoteIPAndPort(conn *net.UDPConn, server *net.UDPAddr) (*net.UDPAddr, error). The horrible (and inaccurate) name aside, this function will return the public IP and port of the net.UDPConn object passed into this function, using the STUN server provided in server.

The below is a wholesome (compilable) example snippet on how to use the function:

package main

import (
    "fmt"
    "net"
    "./stun_c"
)

func main() {
    server, err := net.ResolveUDPAddr("udp", "stun.l.google.com:19302") //by the way, "udpv6" works too
    if (err != nil) {
        fmt.Println(err)
        return
    }

    local_socket, err := net.ListenUDP("udp", nil)
    if (err != nil) {
        fmt.Println(err)
        return
    }

    remote_addr, err := stun_c.RequestRemoteIPAndPort(local_socket, server)
    if (err != nil) {
        fmt.Println(err)
        return
    }

    fmt.Printf("Local socket: %s, Remote socket: %s\n", local_socket.LocalAddr(), remote_addr)
    return
}

The above code is also available in the file test.go.

License

This is licensed under the MIT License.