How do I frame messages for sending over TCP with node.js?

to unframe incoming data in nodejs you can try to use node-bufferlist or node-buffers or create your own FSM manually and feed it with incoming chunks of data

server side is simplier:

function sendPacket(stream, buffer)
{
    var prefix = new Buffer(4);
    var length = buffer.length;
    var offset = 0;
    // serialize 32bit little endian unsigned int
    prefix[offset++] = length & 0xff;
    prefix[offset++] = (length >> 8)  & 0xff );
    prefix[offset++] = (length >> 16)  & 0xff );
    prefix[offset++] = (length >> 24)  & 0xff );
    stream.write(prefix);
    stream.write(buffer);
}

or you can use node v0.5+ buffer.writeUInt32