如何将一系列数据包写入Node.js net.Socket？

Question

Would like to know if there's anything special i need to do to write an array of packets, sequentially to an instance of net.Socket in Node.js.

I'm not sure if writing to the same socket in a for loop would be synchronous or also async.

If it's async, would i have to promisify Socket.write and have the loop set up a .then() chain. I'm already using bluebird for promises.

thanks!

Answer 1

I was also confused by this. Most Node.js examples make it seem like write() is synchronous:

var server = net.createServer(function(socket) {
  socket.write('Hello!');
  socket.end();
});

It turns out the non-callback version of write() actually means write_eventually() . If it can't actually write your data to the socket, it queues it up in memory. Node takes care of writing the queued data out to the socket eventually.

I imagine they did this because callbacks are annoying and this reduces the number of callbacks in your code. The downside is that it uses more memory (see: Socket.bufferSize ).

If you're pushing lots of data, it's more memory-efficient to use the callback version of write() :

"use strict";

var net = require("net")

function writeArray(arrayOfChunks, socket, callback) {
  var i = 0;
  function f() {
    if (i >= arrayOfChunks.length) {
      callback();
    } else {
      socket.write(arrayOfChunks[i++], null, f);
    }
  }
  f()
}

var server = net.createServer((socket) => {
  var arrayOfChunks = ['Hello', ', ', 'world!', '\n'];
  writeArray(arrayOfChunks, socket, () => {
    socket.write('DONE\n', null, () => {
      socket.end();
    })
  })
})

server.listen(9191, () => {
  console.log("Server listening.");
})

But it's 2016, so maybe you can just use async / await and not have to deal with callback/promise nonsense.

Answer 2

Multiple writes are guaranteed to be executed in order.

Requests:Responses are not guaranteed to be mapped 1:1.