C#套接字问题

Question

我在C#中创建一个套接字服务器,在PHP中创建一个客户端.客户端和服务器之间的对话是这样的:

1. 客户连接
2. 服务器发送欢迎消息
3. 客户端发送数据
4. 服务器发送响应
5. (重复步骤3 - 4直到客户端断开连接)

它一直工作到第3步.来自客户端的数据由服务器接收.但是,客户端会一直等待,直到服务器发送响应并最终超时.

这是相关的C#代码:

class Program
{
    private const int CONNECT_QUEUE_LENGTH = 4;

    static void ListenForRequests()
    {
        Socket listenSock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
        listenSock.Bind(new IPEndPoint(IPAddress.Any, 9999));
        listenSock.Listen(CONNECT_QUEUE_LENGTH);
        listenSock.Blocking = true;

        byte[] data = new byte[1024];

        while (true)
        {
            Socket newConnection = listenSock.Accept();
            newConnection.Blocking = true;

            // Create new thread for each request
            var t = new Thread(() => new RequestHandler(newConnection));
            t.Start();
        }
    }
}

class RequestHandler
{
    public RequestHandler(Socket socket)
    {
        Util.WriteToSocket("A message", socket);
        Console.WriteLine("Received: " + Util.ReadSocketToEnd(socket).Length);
        Util.WriteToSocket("Fin!", socket);
    }
}    

static class Util
{ 
    public static string ReadSocketToEnd(Socket newConnection)
    {
        var sb = new StringBuilder();

        byte[] data = new byte[1024];
        int receivedDataLength = newConnection.Receive(data);

        while (receivedDataLength > 0)
        {
            try
            {
                sb.Append(Encoding.UTF8.GetString(data, 0, receivedDataLength));
                receivedDataLength = newConnection.Receive(data);
            }
            catch (SocketException)
            {
                break;
            }
        }

        return sb.ToString();
    }

    public static void WriteToSocket(string message, Socket client)
    {
        byte[] data = Encoding.UTF8.GetBytes(message);
        client.Send(data, SocketFlags.None);
    }
}

这是简单的PHP客户端,没有任何错误处理等:

<?php

$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
$result = socket_connect($socket, '127.0.0.1', 9999);

print 'receiving: ' . chr(10);
print socket_read ($socket, 10) . chr(10);
print 'receive end' . chr(10);


$message = str_repeat("Message to sent", 1000);
socket_write($socket, $message, strlen($message));
print 'message sent' . chr(10);


print 'reading fin' . chr(10); // This is printed, but a response is never received
print socket_read ($socket, 10) . chr(10);
print 'fin read!' . chr(10);

socket_shutdown($socket);

Answer 1

您正在读取套接字,直到读取了所有数据 - 这意味着"直到套接字关闭所有数据".您的PHP客户端正在写入数据,但没有关闭套接字 - 因此服务器正在等待.

TCP套接字提供数据流.没有"当前消息的结束"的概念,这就是你想要的.

处理此问题的三种方法通常是:

• 消息分隔符(例如换行符)
• 消息长度前缀(消息本身之前的消息中的字节数)
• 为每个请求/响应对使用不同的连接

您可能会使用超时读取,并假设如果您在过去5秒内没有看到任何更多数据,那么您已经获得了整个消息 - 但这是脆弱,低效且通常是个坏主意.