多次写入时节点网络数据合并

Question

我正在使用 Node 网络。

客户端多次写入feed时，在服务端收到1条数据。

var net           = require('net');

// SERVER SIDE
var net_port   = 8080; // node net port
var server = net.createServer(function(connection){
   connection.on('data', function(data){
          var str = data.toString();
          console.log("Received, Length: "+str.length); // IT SHOULD be 25 in length
    });
   connection.pipe(connection);
});

server.listen(net_port, function() { 
   console.log('server is listening');
});
// SERVER CODE NED

// ### 客户端

var client = net.connect({port: 8080}, function() {
   console.log('connected to server!');  
});


string = "acdefghijklmnopqrstuvwxyz"; // 25 char
setInterval(function(){
    client.write(string);
    client.write(string);
},1);
setInterval(function(){
    client.write(string);
    client.write(string);
},1);

发送长度为 25 的字符串，但收到时 OUTPUT IS

Received, Length: 25
Received, Length: 25
Received, Length: 75  // merged 3 data
Received, Length: 100 // merged 4 data
Received, Length: 25
Received, Length: 50 // merge 2 times
Received, Length: 75
Received, Length: 25
Received, Length: 25
Received, Length: 25
Received, Length: 100

实际上，在我的实际代码中，我不能使用 split 字符串，因为如果客户端发送String length 100 4 次。所以服务器收到了

Received, Length: 100
Received, Length: 220
Received, Length: 80

如何强制 Node Net 发送和接收实际数据。

小提琴：https://www.mycompiler.io/view/BJGjA87

Answer 1

net.createServer 创建一个 TCP 服务器。 TCP 套接字是基于流的，而不是基于数据报的。他们没有消息边界的概念：一切都只是一个连续的字节流，没有标记来区分哪些片段是一起发送的，哪些是单独发送的。如果您想在通过 TCP 套接字发送的消息之间建立边界，您必须自己划定它们：或者通过假设每条消息必须具有以字节为单位的固定长度，或者通过引入确定一条消息结束位置和另一条消息开始位置的标记。

例如，下面是对您的服务器的简单修改，它为此使用RFC 7464 中定义的 json-seq 格式。从长远来看，您可能会考虑使用诸如ws 之类的库将其设为 WebSocket 服务器。它可能比下面的代码更健壮；这主要只是一个演示。

var net = require('net');

var server = net.createServer(function (connection) {
    var buffer = '';
    
    function receivedMessage(value) {
        console.log('received: ' + JSON.stringify(value));
    }
    
    function protocolError() {
        console.log('protocol error');
        connection.close();
    }
    
    function parseMessages(buf) {
        console.log('parsing ' + buf.length + ' code units worth of messages');
        if (buf.substring(0, 1) !== '\x1e') {
            protocolError();
            return;
        }
        var m, rx = /\x1e([^\x1e]*)/g;
        while (m = rx.exec(buffer)) {
            if (m[1] === '')
                continue;
            try {
                var value = JSON.parse(m[1]);
            } catch (e) {
                if (e instanceof SyntaxError)
                    continue;   // RFC 7464 §2.3
                throw e;
            }
            receivedMessage(value);
        }       
    }
    
    connection.on('data', function (data) {
        buffer += data.toString('utf8');
        console.log(buffer.length + ' code units in the buffer');
        var lastRS = buffer.lastIndexOf('\x1e');
        if (lastRS === 0)
            return;
        var fullMessages = buffer.substring(0, lastRS);
        buffer = buffer.substring(lastRS, buffer.length);
        parseMessages(fullMessages);
        try {
            var value = JSON.parse(buffer);
        } catch (e) {
            if (e instanceof SyntaxError)
                return;  // maybe just truncated; defer error until later
            throw e;
        }
        receivedMessage(value);
        buffer = '';
    });

    connection.on('close', function () {
        console.log('closed');
        parseMessages(buffer);
    });
});

server.listen(8080, function() { 
    console.log('server is listening');
});

这是一个经过适当修改的客户端：

var net = require('net');

var client = net.connect({port: 8080}, function() {
   console.log('connected to server!');  
});

function sendMessage(value) {
    client.write(Buffer.from('\x1e' + JSON.stringify(value) + '\n', 'utf8'));
}

string = 'acdefghijklmnopqrstuvwxyz';

setInterval(function(){
    sendMessage(string);
    sendMessage(string);
}, 1);

setInterval(function(){
    sendMessage(string);
    sendMessage(string);
}, 1);