我做了一个lib，它正好满足了你的需求：https://www.npmjs.com/package/node-easysocket（除了在小端写入4个字节，但很容易修复）
关于你的问题，我们开始：
发送消息比接收要容易得多，你只需要将消息转换为一个ByteArray，并在前面加上一个包含ByteArray + 4大小的整数（4字节Big Endian）：

var buffer = new Buffer("Hello World or a JSON String", "binary");

//create a buffer with +4 bytes
var consolidatedBuffer = new Buffer(4 + buffer.length);

//write at the beginning of the buffer, the total size
consolidatedBuffer.writeInt32BE(buffer.length, 0);

//Copy the message buffer to the consolidated buffer at position 4     (after the 4 bytes about the size)
buffer.copy(consolidatedBuffer, 4);

//Send the consolidated buffer
socket.write(consolidatedBuffer, function(err) {
     if (err) console.log(err)
});

如果你想读取，它会有点复杂，因为你有可能读取拼接成块的缓冲区。
示例：我的缓冲区有10MB的大小，但我的网络连接每秒可以传输约100字节，因此服务器将接收大量数据，您将需要存储它们，直到它完成必要的大小，根据前4字节的长度通知。
Javascript是一种动态语言，所以我可以在socket对象中创建一个运行时属性来存储收集到的块：

socket.on('data', function(data) {
    console.log("server bytes in:"+data.length);
    receive(socket,data);
});

function receive(socket, data){
    //Create a chunk prop if it does not exist
    if(!socket.chunk){
        socket.chunck = {
            messageSize : 0,
            buffer: new Buffer(0),
            bufferStack: new Buffer(0)
        };
    }
    //store the incoming data
    socket.chunck.bufferStack = Buffer.concat([socket.chunck.bufferStack, data]);
    //this is to check if you have a second message incoming in the tail of the first
    var reCheck = false;
    do {
        reCheck = false;
        //if message size == 0 you got a new message so read the message size (first 4 bytes)
        if (socket.chunck.messageSize == 0 && socket.chunck.bufferStack.length >= 4) {
            socket.chunck.messageSize = socket.chunck.bufferStack.readInt32BE(0);
        }

        //After read the message size (!= 0) and the bufferstack is completed and/or the incoming data contains more data (the next message)
        if (socket.chunck.messageSize != 0 && socket.chunck.bufferStack.length >= socket.chunck.messageSize + 4) {
            var buffer = socket.chunck.bufferStack.slice(4, socket.chunck.messageSize + 4);
            socket.chunck.messageSize = 0;
            socket.chunck.bufferStack = socket.chunck.bufferStack.slice(buffer.length + 4);
            onMessage(socket, buffer);
            //if the stack contains more data after read the entire message, maybe you got a new message, so it will verify the next 4 bytes and so on...
            reCheck = socket.chunck.bufferStack.length > 0;
        }
    } while (reCheck);
}

function onMessage(socket, buffer){
    console.log("message received from: "+socket+" with data:"+buffer.toString()+");
}