javascript - Node js 从 tcp 套接字 net.createServer 读取特定消息

Question

var net = require('net');

var HOST = '0.0.0.0';
var PORT = 5000;

// Create a server instance, and chain the listen function to it
// The function passed to net.createServer() becomes the event handler for the 'connection' event
// The sock object the callback function receives UNIQUE for each connection
net.createServer(function(sock) {

// We have a connection - a socket object is assigned to the connection automatically
console.log('CONNECTED: ' + sock.remoteAddress +':'+ sock.remotePort);

// Add a 'data' event handler to this instance of socket
sock.on('data', function(data) {

    console.log('DATA ' + sock.remoteAddress + ': ' + data);
    // Write the data back to the socket, the client will receive it as data from the server
    if (data === "exit") {
        console.log('exit message received !')
    }

});

// Add a 'close' event handler to this instance of socket
sock.on('close', function(data) {
    console.log('CLOSED: ' + sock.remoteAddress +' '+ sock.remotePort);
});

}).listen(PORT, HOST);

console.log('Server listening on ' + HOST +':'+ PORT);

无论我怎么尝试，我都得不到:

    if (data === "exit") {
        console.log('exit message received !')
    }

工作，总是假的。

我正在通过 telnet 连接并发送“exit”，然后服务器应该进入“if”循环并说“exit message received”。这永远不会发生，有人可以解释一下吗？谢谢

Answer 1

那是因为数据不是字符串，如果您尝试与 === 进行比较，您将得到 false，因为类型不匹配。 要解决它，您应该将数据对象与简单的 == 进行比较，或者在绑定(bind)数据事件之前使用 socket.setEncoding('utf8')。

https://nodejs.org/api/net.html#net_event_data

var net = require('net');
var HOST = '0.0.0.0';
var PORT = 5000;

net.createServer(function(sock) {
    console.log('CONNECTED:',sock.remoteAddress,':',sock.remotePort);
    sock.setEncoding("utf8"); //set data encoding (either 'ascii', 'utf8', or 'base64')
    sock.on('data', function(data) {
        console.log('DATA',sock.remoteAddress,': ',data,typeof data,"===",typeof "exit");
        if(data === "exit") console.log('exit message received !');
    });

}).listen(PORT, HOST, function() {
    console.log("server accepting connections");
});

Note. If the data received is going to be big you should concatenate and handle the message comparison at the end of it. Check other questions to handle those cases:

Node.js net library: getting complete data from 'data' event