javascript Node.js 网络库：从“数据”事件中获取完整数据

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

提问by coding_hero

I've searched around, and either can't find the exact question I'm trying to answer, or I need someone to explain it to me like I'm 5.

我四处搜索，要么找不到我想要回答的确切问题，要么我需要有人像我 5 岁一样向我解释。

Basically, I have a Node.js script using the Net library. I'm connecting to multiple hosts, and sending commands, and listening for return data.

基本上，我有一个使用 Net 库的 Node.js 脚本。我连接到多个主机，发送命令，并侦听返回数据。

var net = require('net');

var nodes = [
    'HOST1,192.168.179.8',
    'HOST2,192.168.179.9',
    'HOST3,192.168.179.10',
    'HOST4,192.168.179.11'
];

function connectToServer(tid, ip) {
    var conn = net.createConnection(23, ip);
    conn.on('connect', function() {
        conn.write (login_string);  // login string hidden in pretend variable
    });
    conn.on('data', function(data) {
        var read = data.toString();
        if (read.match(/Login Successful/)) {
            console.log ("Connected to " + ip);
            conn.write(command_string);
        }

        else if (read.match(/Command OK/)) { // command_string returned successful,
                                                    // read until /\r\nEND\r\n/

                    // First part of data comes in here
            console.log("Got a response from  " + ip + ':' + read);
        }
        else {
                 //rest of data comes in here
             console.log("Atonomous message from " + ip + ':' + read);
        }
    });
    conn.on('end', function() {
        console.log("Lost conncection to " + ip + "!!");
    });
    conn.on('error', function(err) {
        console.log("Connection error: " + err + " for ip " + ip);
    });
}

nodes.forEach(function(node) {
    var nodeinfo = node.split(",");
    connectToServer(nodeinfo[0], nodeinfo[1]);
});

The data ends up being split into two chunks. Even if I store the data in a hash and append the first part to the remainder when I read the /\r\nEND\r\n/ delimiter, there's a chunk missing out of the middle. How do I properly buffer the data in order to make sure I get the complete message from the stream?

数据最终被分成两个块。即使我在读取 /\r\nEND\r\n/ 分隔符时将数据存储在散列中并将第一部分附加到剩余部分，中间也会丢失一个块。如何正确缓冲数据以确保从流中获得完整的消息？

EDIT: Ok, this seems to be working better:

编辑：好的，这似乎工作得更好：

function connectToServer(tid, ip) {
        var conn = net.createConnection(23, ip);

        var completeData = '';

        conn.on('connect', function() {
                conn.write (login_string);
        });
        conn.on('data', function(data) {
                var read = data.toString();

                if (read.match(/Login Successful/)) {
                        console.log ("Connected to " + ip);

                        conn.write(command_string);
                }
                else {
                        completeData += read;
                }

                if (completeData.match(/Command OK/)) {
                        if (completeData.match(/\r\nEND\r\n/)) {
                                console.log("Response: " + completeData);
                        }
                }
        });
        conn.on('end', function() {
                console.log("Connection closed to " + ip );
        });
        conn.on('error', function(err) {
                console.log("Connection error: " + err + " for ip " + ip);
        });
}

My biggest problem was apparently a logic error. I was either waiting for the chunk that began the reply, or the chunk that ended it. I wasn't saving everything in-between.

我最大的问题显然是逻辑错误。我要么在等待开始回复的块，要么等待结束它的块。我并没有保存中间的所有内容。

I guess if I wanted to get all Node-ish about it, I should fire an event whenever a complete message came in (beginning with a blank line, ending with 'END' on a line by itself), and do the processing there.

我想如果我想获得所有关于它的 Node-ish，我应该在收到完整消息时触发一个事件（以空行开头，以 'END' 结束），并在那里进行处理。

采纳答案by coding_hero

My problem was a logic problem. I was either looking for the chunk that began the message, or the chunk that ended the message, and ignoring everything in between. I guess expected the entirety of the reply to come in in one or two chunks.

我的问题是逻辑问题。我要么在寻找开始消息的块，要么寻找结束消息的块，并忽略中间的所有内容。我猜想整个回复会分成一两块。

Here's the working code, pasted from above. There's probably a more Node-ish way of doing it (I should really emit an event for each chunk of information), but I'll mark this as the answer unless someone posts a better version by this time tomorrow.

这是从上面粘贴的工作代码。可能有一种更像 Node 的方式来做（我真的应该为每个信息块发出一个事件），但我会将其标记为答案，除非有人在明天这个时候发布更好的版本。

function connectToServer(tid, ip) {
        var conn = net.createConnection(23, ip);

        var completeData = '';

        conn.on('connect', function() {
                conn.write (login_string);
        });
        conn.on('data', function(data) {
                var read = data.toString();

                if (read.match(/Login Successful/)) {
                        console.log ("Connected to " + ip);

                        conn.write(command_string);
                }
                else {
                        completeData += read;
                }

                if (completeData.match(/Command OK/)) {
                        if (completeData.match(/\r\nEND\r\n/)) {
                                console.log("Response: " + completeData);
                        }
                }
        });
        conn.on('end', function() {
                console.log("Connection closed to " + ip );
        });
        conn.on('error', function(err) {
                console.log("Connection error: " + err + " for ip " + ip);
        });
}

回答by ChrisCM

You shouldn't do anything with the data you recieve, until you receive the end event. The end callback means that all data chunks have been sent through the stream to your callbacks. If data comes in more than one chunk, you need to create a variable within your function closure to store this data to. Most programs can work just fine ignoring this fact, because data usually comes across in one chunk. But sometimes it doesn't. It doesn't even necessarily depend on the amount of data. If you're in a situation where this is happening, I created an example that demos how to handle it. I basically used your code, but removed all the fluff... this is just demoing the logic you need to collect all the data and do work on it.

在收到结束事件之前，您不应该对收到的数据做任何事情。结束回调意味着所有数据块都已通过流发送到您的回调。如果数据来自多个块，则需要在函数闭包中创建一个变量来存储这些数据。大多数程序可以在忽略这一事实的情况下正常工作，因为数据通常出现在一个块中。但有时不会。它甚至不一定取决于数据量。如果您遇到这种情况，我创建了一个示例来演示如何处理它。我基本上使用了您的代码，但删除了所有绒毛……这只是演示收集所有数据并对其进行处理所需的逻辑。

function connectToServer(tid, ip) {
    var conn = net.createConnection(23, ip);
    var completeData = '';

    conn.on('connect', function() {
        conn.write (login_string);  // login string hidden in pretend variable
    });
    conn.on('data', function(data) {
        completeData += data;
        var dataArray = completeData.split('your delimiter');
        if(dataArray.size > 1) { //If our data was split into several pieces, we have a complete chunk saved in the 0th position in the array
            doWorkOnTheFirstHalfOfData(dataArray[0]);
            completeData = dataArray[1];// The second portion of data may yet be incomplete, thise may need to be more complete logic if you can get more than one delimeter at a time...
        }
    });
    conn.on('end', function() {
        //do stuff with the "completeData" variable in here.
    });
}