javascript - Nodejs - 让客户端套接字在 5 秒超时后重试

Question

刚开始使用 node.js 编程并编写一个 tcp 套接字客户端。

我想让客户端连接到服务器。如果服务器不可用(即服务器不存在于约定的端口)，我希望客户端超时并在超时后重新连接。

我有这段代码，但它卡在第二个 client.connect 上。怎么了？

var net = require('net');
var HOST = '127.0.0.1';
var PORT = 9000;
var client = new net.Socket();

client.connect(PORT, HOST, function(){
    console.log('CONNECTED TO: ' + HOST + ':' + PORT);
    client.write('I am Superman!');
});

client.on('error', function(e) {
    while (e.code == 'ECONNREFUSED') {
        console.log('Is the server running at ' + PORT + '?');`

        socket.setTimeout(1000, function() {
            console.log('Timeout for 5 seconds before trying port:' + PORT + ' again');
        }

        client.connect(PORT, HOST, function(){
            console.log('CONNECTED TO: ' + HOST + ':' + PORT);
            client.write('I am the inner superman');
        });
    }); 
});

更新代码:

var net = require('net');
var HOST = '127.0.0.1';
var PORT = 9000;
var client = new net.Socket();

client.connect(PORT, HOST, function(){
    console.log('CONNECTED TO: ' + HOST + ':' + PORT);
    client.write('I am Superman');
});

client.on('error', function(e) {

    while (e.code == 'ECONNREFUSED') {
        console.log('Is the server running at ' + PORT + '?');

        client.setTimeout(4000, function() {

            client.connect(PORT, HOST, function() {
                console.log('CONNECTED TO: ' + HOST + ':' + PORT);
                client.write('I am inner Superman');
            });         

            console.log('Timeout for 5 seconds before trying port:' + PORT + ' again');
        });
    }
});

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

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

使用更新后的代码，超时似乎没有生效。当我在没有相应服务器的情况下启动此客户端时，结果如下所示，没有等待 4 秒。

Is the server running at 9000?
Is the server running at 9000?
Is the server running at 9000?
Is the server running at 9000?
…

更新(吠错树了？)

我回过头来看socket.on('error')事件，发现错误后立即调用了close事件。所以代码将关闭 tcpclient 而无需等待 4 秒。有更好的想法吗？

Answer 1

你的超时被逆转了。

应该看起来像:

var net = require('net');
var HOST = '127.0.0.1';
var PORT = 9000;
var client = new net.Socket();

client.connect(PORT, HOST, function(){
    console.log('CONNECTED TO: ' + HOST + ':' + PORT);
    client.write('I am Superman!');
});

client.on('error', function(e) {
    if(e.code == 'ECONNREFUSED') {
        console.log('Is the server running at ' + PORT + '?');

        client.setTimeout(4000, function() {
            client.connect(PORT, HOST, function(){
                console.log('CONNECTED TO: ' + HOST + ':' + PORT);
                client.write('I am the inner superman');
            });
        });

        console.log('Timeout for 5 seconds before trying port:' + PORT + ' again');

    }   
});
client.on('data', function(data) {
    console.log('DATA: ' + data);
    client.destroy();
});
client.on('close', function() {
    console.log('Connection closed');
});

超时后要运行的函数是回调。那就是等待执行的那个。

此外，将您的 while 更改为 if，该条件在单个错误事件期间不会更改。你的括号和括号不匹配。