因此，请使用net软件包在NodeJs中重用EADDR

Question

我有两个后端。后端A和后端B.
后端B使用运行在端口4243上的套接字服务器发送和接收信息

然后，使用后端A，我需要捕获该信息并保存它。但我还必须在后端a上有一个套接字服务器，在端口4243上运行

问题是，当我在运行后端B之后运行后端A时，我收到错误“EADDRINUSE”，因为我在两个应用程序上使用相同的主机：端口

如果，对于后端A，我使用Python，那么问题就会消失，因为我有一个名为SO_REUSEADDR的套接字配置
这里我们有一些例子：

• https://www.programcreek.com/python/example/410/socket.SO_REUSEADDR
• https://subscription.packtpub.com/book/networking-and-servers/9781849513463/1/ch01lvl1sec18/reusing-socket-addresses

但是，我想使用JavaScript对后端A进行编码，所以我使用net package对套接字进行编码，但由于“EADDRINUSE”错误，我无法让它工作

NodeJS文档说“All sockets in Node set SO_REUSEADDR already”，但它似乎对我不起作用

这是我目前的代码：

// Step 0: Create the netServer and the netClient

console.log(`[DEBUG] Server will listen to: ${HOST}:${PORT}`);
console.log(`[DEBUG] Server will register with: ${AGENT_ID}`);

const netServer = net.createServer((c) => {
  console.log('[netServer] Client connected');

  c.on('message', (msg) => {
    console.log('[netServer] Received `message`, MSG:', msg.toString());
  });

  c.on('*', (event, msg) => {
    console.log('[netServer] Received `*`, EVENT:', event);
    console.log('[netServer] Received `*`, MSG:', msg);
  });

}).listen({
  host: HOST, // 'localhost',
  port: PORT, // 4243,
  family: 4, // ipv4, same as socket.AF_INET for python
});

// Code copied from nodejs documentation page (doesn't make any difference)
netServer.on('error', function (e) {
  if (e.code == 'EADDRINUSE') {
    console.log('Address in use, retrying...');
    setTimeout(function () {
      netServer.close();
      netServer.listen(PORT, HOST);
    }, 1000);
  }
});

const netClient = net.createConnection(PORT, HOST, () => {
  console.log('[netClient] Connected');
});

// Step 1: Register to instance B of DTN with agent ID 'bundlesink'

netClient.write(serializeMessage({
  messageType: AAPMessageTypes.REGISTER,
  eid: AGENT_ID,
}));

使用此代码，我在终端中获得以下输出：

但是，使用Python代码，套接字成功连接：

我不知道该怎么办：（
我希望我能得到一些帮助

---

编辑1

顺便说一下，lsof命令为JavaScript后端抛出以下输出：

Python后端的另一个输出：

---

编辑2

这似乎确实是JavaScript的问题。I also found this snippet：

var net = require('net');

function startServer(port, host, callback) {
    var server = net.createServer();
    server.listen(port, host, function() {
        callback(undefined, server);
    });
    server.on('error', function(error) {
        console.error('Ah damn!', error);
        callback(error);
    });
}

startServer(4000, '0.0.0.0', function(error, wildcardServer) {
    if (error) return;
    startServer(4000, '127.0.0.1', function(error, localhostServer) {
        if (error) return;
        console.log('Started both servers!');
    });
});

从本帖： https://medium.com/@eplawless/node-js-is-a-liar-sometimes-8a28196d56b6

正如作者所说：

Well, that prints “Started both servers!” which is exactly what we don’t want.

但对我来说，我没有打印它，而是得到了一个错误：

Ah damn! Error: listen EADDRINUSE: address already in use 127.0.0.1:4000
    at Server.setupListenHandle [as _listen2] (node:net:1319:16)
    at listenInCluster (node:net:1367:12)
    at doListen (node:net:1505:7)
    at processTicksAndRejections (node:internal/process/task_queues:84:21) {
  code: 'EADDRINUSE',
  errno: -98,
  syscall: 'listen',
  address: '127.0.0.1',
  port: 4000
}

我真的无法运行并打印“已启动两台服务器！”。
因为这就是我想要我的代码做的

---

编辑3

这是Python服务器套接字：https://gitlab.com/d3tn/ud3tn/-/blob/master/tools/aap/aap_receive.py

这是重要的部分：

addr = (args.tcp[0], int(args.tcp[1])) # args.tcp[0] = "localhost", args.tcp[1] = "4243"
with AAPTCPClient(address=addr) as aap_client:
  aap_client.register(args.agentid) # args.agentid = "bundlesink"
  run_aap_recv(aap_client, args.count, args.verify_pl)

它创建了一个AAPTCPClient，而AAPTCPClient所做的唯一事情是：

def __init__(self, socket, address):
  self.socket = socket
  self.address = address
  self.node_eid = None
  self.agent_id = None

def register(self, agent_id=None):
  """Attempt to register the specified agent identifier.

  Args:
    agent_id: The agent identifier to be registered. If None,
        uuid.uuid4() is called to generate one.
  """
  self.agent_id = agent_id or str(uuid.uuid4())
  logger.info(f"Sending REGISTER message for '{agent_id}'...")
  msg_ack = self.send(
    AAPMessage(AAPMessageType.REGISTER, self.agent_id)
  )
  assert msg_ack.msg_type == AAPMessageType.ACK
  logger.info("ACK message received!")

def send(self, aap_msg):
  """Serialize and send the provided `AAPMessage` to the AAP endpoint.

  Args:
      aap_msg: The `AAPMessage` to be sent.
  """
  self.socket.send(aap_msg.serialize())
  return self.receive()

def receive(self):
  """Receive and return the next `AAPMessage`."""
  buf = bytearray()
  msg = None
  while msg is None:
    data = self.socket.recv(1)
    if not data:
      logger.info("Disconnected")
      return None
    buf += data
    try:
      msg = AAPMessage.parse(buf)
    except InsufficientAAPDataError:
      continue
  return msg

我没有看到任何绑定，我也不明白为什么python代码可以调用“socket.recv”，但在我的JavaScript代码中我不能调用“netServer.listen”。我认为应该是一样的

---

Answer 1

有些事情需要澄清。 1.）客户端使用绑定系统调用，内核在其中自动选择源端口

它通过检查sys local\u portrange sysctl设置来实现

1.如果要将客户端绑定到静态源端口，请确保选择本地端口范围之外的TCP端口

2.）您不能订阅事件“*”，而是必须订阅事件“数据””才能接收消息

为了获得最佳实践，您还应在出现错误时订阅“error”事件

这些链接将让您立即开始：

How do SO_REUSEADDR and SO_REUSEPORT differ?

https://idea.popcount.org/2014-04-03-bind-before-connect/

因此，对于所有想使用node.js深入研究网络的初学者来说

工作服务器示例：

    // Step 0: Create the netServer and the netClient
//

var HOST = 'localhost';
var PORT = 4243;
var AGENT_ID = 'SO_REUSEADDR DEMO';
var net = require('net');

console.log(`[DEBUG] Server will listen to: ${HOST}:${PORT}`);
console.log(`[DEBUG] Server will register with: ${AGENT_ID}`);

const netServer = net.createServer((c) => {
  console.log('[netServer] Client connected');

  c.on('data', (msg) => {
    console.log('[netServer] Received `message`, MSG:', msg.toString());
  });

  c.on('end', () => {
    console.log('client disconnected');
  });

  c.on('error', function (e) {
    console.log('Error: ' + e.code);
  });

  c.write('hello\r\n');
  c.pipe(c);

}).listen({
  host: HOST,
  port: PORT,
  family: 4, // ipv4, same as socket.AF_INET for python
});

// Code copied from nodejs documentation page (doesn't make any difference)
netServer.on('error', function (e) {
   console.log('Error: ' + e.code);
  if (e.code == 'EADDRINUSE') {
    console.log('Address in use, retrying...');
    setTimeout(function () {
      netServer.close();
      netServer.listen(HOST, PORT);
    }, 1000);
  }
  if ( e.code = 'ECONNRESET' ){
    console.log('Connection reset by peer...');
      setTimeout(function () {
        netServer.close();
        netServer.listen(HOST, PORT);
      }, 1000);
  }

});

客户：

/* Or use this example tcp client written in node.js.  (Originated with
example code from
http://www.hacksparrow.com/tcp-socket-programming-in-node-js.html.) */

var net = require('net');
var HOST = 'localhost';
var PORT = 4243;

var client = new net.Socket();
client.setTimeout(3000);
client.connect(PORT, HOST, function() {
    console.log("Connected to " + client.address().address + " Source Port: " + client.address().port + " Family: " + client.address().family);
    client.write('Hello, server! Love, Client.');
});

client.on('data', function(data) {
    console.log('Received: ' + data);
    client.end();
});

client.on('error', function(e) {
    console.log('Error: ' + e.code);
});

client.on('timeout', () => {
  console.log('socket timeout');
  client.end();
});

client.on('close', function() {
    console.log('Connection closed');
});

最佳汉内斯酒店

Answer 2

斯蒂芬·乌尔里希是完全正确的

在我的JavaScript代码中，我试图创建一个服务器来侦听端口4243
但是你不需要有一个服务器来监听某个端口，你也可以用一个客户端来监听！（至少我是这么理解的）

您可以按以下方式创建客户端连接：

const netClient = net.createConnection(PORT, HOST, () => {
  console.log('[netClient] Connected');
});

netClient.on('data', (data) => {
  console.log('[netClient] Received data:', data.toString('utf8'));
});

使用“client.on”，您还可以接收消息，就像它是服务器一样

我希望这对其他人有用