TCP客戶端/服務器數據包丟失

Question

我目前正在使用NodeJS開發TCP客戶端和服務器。 但是，為什么在這里出現“丟包”現象？ 看截圖： http : //i.imgur.com/YoCtAAV.png

客戶代碼：

console.log('Starting Client...')

var net = require('net')

var client = new net.Socket()

client.connect(3000, '127.0.0.1', function() {
    console.log('Connected to server on 127.0.0.1:3000')

    var packet
    for (i = 0; i <= 20; i++) {
        packet = new Buffer(4)
        packet.writeUInt32LE(i, 0)
        client.write(packet)

        console.log('Packet Counter sent: ' + i)
    }
})

client.on('error', function(e) {
    if(e.code == 'ECONNRESET') {
        console.error('Connection abnormally closed')
    } else if(e.code == 'ECONNREFUSED') {
        console.error('Connection refused. Server down?')
    } else {
        console.error('Unhandled error occured:')
        console.error(e)
    }
})

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

服務器代碼：

console.log('Starting Server...')

var net = require('net')

var server = net.createServer(function(session) {
    console.log('Connection opened')

    session.on('data', function(packet) {
        var packet_counter = packet.readUInt32LE(0)

        console.log('Packet Counter received: ' + packet_counter)
    })

    session.on('error', function(e) {
        if(e.code == 'ECONNRESET') {
            console.log('Connection closed')
        } else {
            console.error('Unhandled session error occured:')
            console.error(e)
        }
    })

    session.on('end', function() {
        console.log('Connection closed')
    })
})

server.on('error', function(e) {
    if(e.code == 'EADDRINUSE') {
        console.error('Port 3000 already in use')
    } else {
        console.error('Unhandled server error occured:')
        console.error(e)
    }
})

server.listen(3000, '0.0.0.0')

console.log('Server started on 0.0.0.0:3000')

如何解決此問題並在服務器日志中獲得預期的輸出？

Packet Counter received: 0
Packet Counter received: 1
Packet Counter received: 2
Packet Counter received: 3
Packet Counter received: 4
Packet Counter received: 5
Packet Counter received: 6
Packet Counter received: 7
Packet Counter received: 8
Packet Counter received: 9
Packet Counter received: 10
Packet Counter received: 11
Packet Counter received: 12
Packet Counter received: 13
Packet Counter received: 14
Packet Counter received: 15
Packet Counter received: 16
Packet Counter received: 17
Packet Counter received: 18
Packet Counter received: 19
Packet Counter received: 20

Answer 1

可能沒有數據包丟失。 TCP只是不會發送您期望的數據包。 它發送一個流-就像一個文件。 文件不是由數據包組成，而是由字節組成。 TCP模擬此行為。 因此，當您發送兩個“數據包”時，TCP層（TCP庫，操作系統，路由器或ISP）可能會將它們組合為一個TCP數據包，或者將它們分解為多個TCP數據包。

要真正知道是否有數據包丟失，您必須檢查接收數據的總大小與發送數據的總大小。

正是這種類似於文件流的行為，這就是人們創建更高層協議（例如HTTP或FTP或Bittorrent）的原因，以便對數據包的開始和結束位置進行編碼。

TCP不會為您做這件事。