Listens for UDP packets, sending the stream to stdout and also teeing it to another port on the local machine.

teegram.js

#!/usr/bin/env node

// Listens for UDP packets, sending the stream to stdout and
//  also teeing it to another port on the local machine.
// 
// Usage: teegram.js LISTEN_PORT TEE_PORT


var dgram  = require('dgram');


var DEBUG       = false
,   LISTEN_PORT = parseInt(process.argv[1])
,   TEE_PORT    = parseInt(process.argv[2])
;

if (!(LISTEN_PORT > 0 && TEE_PORT > 0)) {
    console.error("Usage: teegram.js LISTEN_PORT TEE_PORT");
    console.error("  Invalid port(s): LISTEN_PORT="+LISTEN_PORT+"; TEE_PORT="+TEE_PORT);
    process.exit(1);
}


var server = dgram.createSocket("udp4")
,   client = dgram.createSocket("udp4")
;

server.on("message", function(msg, rinfo){
    DEBUG && console.error([
        new Date(), 
        rinfo.address + ":" + rinfo.port,
        String(msg)
    ].join('\t'));
    
    // Log to stdout
    console.log(String(msg));
    
    // Tee to TEE_PORT
    client.send(msg, 0, msg.length, TEE_PORT, 'localhost', function(err, bytes){
        err && DEBUG && console.error(err);
    });
});

DEBUG && server.on("listening", function(){
    var adr = server.address();
    console.error("Starting UDP Server! (" + adr.address + ":" + adr.port + ")");
});

server.bind(LISTEN_PORT);