C# TCP 服务器缓冲区
本文关键字：缓冲区 服务器 TCP | 更新日期: 2023-09-27 18:33:37
我一直在尝试让它工作一段时间，我什至搜索了大部分论坛，但到目前为止我什么都没有。
我的问题：Process_send完美地工作，因为我的客户端可以接收服务器发送的所有内容。但是，当客户端说出某些内容时，process_receive函数中的缓冲区将返回为 null，即使 TransferredBytes 属性显示"46"，这是它应该的样子。
请让我知道如何解决此问题。谢谢！
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.Threading;
using System.Net;
namespace MonkeySyncServer
{
public partial class ServerForm : Form
{
public ServerForm()
{
InitializeComponent();
}
private void btn_startServer_Click(object sender, EventArgs e)
{
Server s = new Server(100, 1024);
s.Init();
s.Start(new IPEndPoint(IPAddress.Any, 1000));
}
}
/// <summary>
/// Implements the connection logic for the socket server.
/// </summary>
class Server
{
private int m_numConnections; // the maximum number of connections the sample is designed to handle simultaneously
private int m_receiveBufferSize;// buffer size to use for each socket I/O operation
BufferManager m_bufferManager; // represents a large reusable set of buffers for all socket operations
const int opsToPreAlloc = 2; // read, write (don't alloc buffer space for accepts)
Socket listenSocket; // the socket used to listen for incoming connection requests
// pool of reusable SocketAsyncEventArgs objects for write, read and accept socket operations
SocketAsyncEventArgsPool m_readWritePool;
int m_totalBytesRead; // counter of the total # bytes received by the server
int m_numConnectedSockets; // the total number of clients connected to the server
Semaphore m_maxNumberAcceptedClients;
/// <summary>
/// Create an uninitialized server instance. To start the server listening for connection requests
/// call the Init method followed by Start method
/// </summary>
/// <param name="numConnections">the maximum number of connections the sample is designed to handle simultaneously</param>
/// <param name="receiveBufferSize">buffer size to use for each socket I/O operation</param>
public Server(int numConnections, int receiveBufferSize)
{
m_totalBytesRead = 0;
m_numConnectedSockets = 0;
m_numConnections = numConnections;
m_receiveBufferSize = receiveBufferSize;
// allocate buffers such that the maximum number of sockets can have one outstanding read and
//write posted to the socket simultaneously
m_bufferManager = new BufferManager(receiveBufferSize * numConnections * opsToPreAlloc,
receiveBufferSize);
m_readWritePool = new SocketAsyncEventArgsPool(numConnections);
m_maxNumberAcceptedClients = new Semaphore(numConnections, numConnections);
}
/// <summary>
/// Initializes the server by preallocating reusable buffers and context objects. These objects do not
/// need to be preallocated or reused, by is done this way to illustrate how the API can easily be used
/// to create reusable objects to increase server performance.
/// </summary>
public void Init()
{
// Allocates one large byte buffer which all I/O operations use a piece of. This gaurds
// against memory fragmentation
m_bufferManager.InitBuffer();
// preallocate pool of SocketAsyncEventArgs objects
SocketAsyncEventArgs readWriteEventArg;
for (int i = 0; i < m_numConnections; i++)
{
//Pre-allocate a set of reusable SocketAsyncEventArgs
readWriteEventArg = new SocketAsyncEventArgs();
readWriteEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(IO_Completed);
readWriteEventArg.UserToken = new AsyncUserToken();
// assign a byte buffer from the buffer pool to the SocketAsyncEventArg object
m_bufferManager.SetBuffer(readWriteEventArg);
// add SocketAsyncEventArg to the pool
m_readWritePool.Push(readWriteEventArg);
}
}
/// <summary>
/// Starts the server such that it is listening for incoming connection requests.
/// </summary>
/// <param name="localEndPoint">The endpoint which the server will listening for conenction requests on</param>
public void Start(IPEndPoint localEndPoint)
{
// create the socket which listens for incoming connections
listenSocket = new Socket(localEndPoint.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
listenSocket.Bind(localEndPoint);
// start the server with a listen backlog of 100 connections
listenSocket.Listen(100);
// post accepts on the listening socket
StartAccept(null);
}
/// <summary>
/// Begins an operation to accept a connection request from the client
/// </summary>
/// <param name="acceptEventArg">The context object to use when issuing the accept operation on the
/// server's listening socket</param>
public void StartAccept(SocketAsyncEventArgs acceptEventArg)
{
if (acceptEventArg == null)
{
acceptEventArg = new SocketAsyncEventArgs();
acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed);
}
else
{
// socket must be cleared since the context object is being reused
acceptEventArg.AcceptSocket = null;
}
m_maxNumberAcceptedClients.WaitOne();
bool willRaiseEvent = listenSocket.AcceptAsync(acceptEventArg);
if (!willRaiseEvent)
{
ProcessAccept(acceptEventArg);
}
}
/// <summary>
/// This method is the callback method associated with Socket.AcceptAsync operations and is invoked
/// when an accept operation is complete
/// </summary>
void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e)
{
ProcessAccept(e);
}
private void ProcessAccept(SocketAsyncEventArgs e)
{
Interlocked.Increment(ref m_numConnectedSockets);
Console.WriteLine("Client connection accepted. There are {0} clients connected to the server",
m_numConnectedSockets);
// Get the socket for the accepted client connection and put it into the
//ReadEventArg object user token
SocketAsyncEventArgs readEventArgs = m_readWritePool.Pop();
((AsyncUserToken)readEventArgs.UserToken).Socket = e.AcceptSocket;
byte[] d = e.Buffer;
// As soon as the client is connected, post a receive to the connection
bool willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs);
d = d;
if (!willRaiseEvent)
{
ProcessReceive(readEventArgs);
}
// Accept the next connection request
StartAccept(e);
}
/// <summary>
/// This method is called whenever a receive or send opreation is completed on a socket
/// </summary>
/// <param name="e">SocketAsyncEventArg associated with the completed receive operation</param>
void IO_Completed(object sender, SocketAsyncEventArgs e)
{
// determine which type of operation just completed and call the associated handler
switch (e.LastOperation)
{
case SocketAsyncOperation.Receive:
ProcessReceive(e);
break;
case SocketAsyncOperation.Send:
ProcessSend(e);
break;
default:
throw new ArgumentException("The last operation completed on the socket was not a receive or send");
}
}
private bool sendToClient(AsyncUserToken token, SocketAsyncEventArgs e, string s)
{
// Send 'Hello World' to the server
byte[] buffer = Encoding.UTF8.GetBytes(s);
Console.WriteLine("Sending: " + buffer.Length + " bytes of data");
e.SetBuffer(buffer, 0, buffer.Length);
bool willRaiseEvent = token.Socket.SendAsync(e);
return willRaiseEvent;
}
/// <summary>
/// This method is invoked when an asycnhronous receive operation completes. If the
/// remote host closed the connection, then the socket is closed. If data was received then
/// the data is echoed back to the client.
/// </summary>
private void ProcessReceive(SocketAsyncEventArgs e)
{
m_bufferManager.SetBuffer(e);
// check if the remote host closed the connection
AsyncUserToken token = (AsyncUserToken)e.UserToken;
if (e.BytesTransferred > 0 && e.SocketError == SocketError.Success)
{
//increment the count of the total bytes receive by the server
Interlocked.Add(ref m_totalBytesRead, e.BytesTransferred);
// Console.WriteLine("The server has read a total of {0} bytes", m_totalBytesRead);
Console.WriteLine("Received from client: {0}", Encoding.UTF8.GetString(e.Buffer, 0, e.BytesTransferred));
byte[] data = new byte[1024];
data = e.Buffer;
String dataString = Encoding.UTF8.GetString(data);
if (dataString.StartsWith("hello"))
{
token.encryptionKey = Encoding.UTF8.GetString(data).Substring(5, dataString.IndexOf("world") - 5);
Console.WriteLine(token.encryptionKey);
}
/* bool willRaiseEvent = sendToClient(token, e, "hello world");
if (!willRaiseEvent)
{
ProcessSend(e);
}*/
}
else
{
CloseClientSocket(e);
}
}
/// <summary>
/// This method is invoked when an asynchronous send operation completes. The method issues another receive
/// on the socket to read any additional data sent from the client
/// </summary>
/// <param name="e"></param>
private void ProcessSend(SocketAsyncEventArgs e)
{
if (e.SocketError == SocketError.Success)
{
// done echoing data back to the client
AsyncUserToken token = (AsyncUserToken)e.UserToken;
// read the next block of data send from the client
bool willRaiseEvent = token.Socket.ReceiveAsync(e);
if (!willRaiseEvent)
{
// e.SetBuffer(e.Offset, listenSocket.ReceiveBufferSize);
// ProcessReceive(e);
}
}
else
{
CloseClientSocket(e);
}
}
private void CloseClientSocket(SocketAsyncEventArgs e)
{
AsyncUserToken token = e.UserToken as AsyncUserToken;
// close the socket associated with the client
try
{
token.Socket.Shutdown(SocketShutdown.Send);
}
// throws if client process has already closed
catch (Exception) { }
token.Socket.Close();
// decrement the counter keeping track of the total number of clients connected to the server
Interlocked.Decrement(ref m_numConnectedSockets);
m_maxNumberAcceptedClients.Release();
Console.WriteLine("A client has been disconnected from the server. There are {0} clients connected to the server", m_numConnectedSockets);
// Free the SocketAsyncEventArg so they can be reused by another client
m_readWritePool.Push(e);
}
}
}
只是基于代码的疯狂猜测。我建议您使用调试器逐步完成此代码，当您这样做时，答案应该很清楚。
这些行是可疑的：
byte[] data = new byte[1024];
data = e.Buffer; // reassigns data, so that byte[1024] gets ignored.
String dataString = Encoding.UTF8.GetString(data); // Ignores the e.Offset value.
我的猜测是缓冲区初始化为零，但由于我不知道的原因，套接字数据没有读入缓冲区的开头，而是在其他地方读取。UTF8 编码器将 0 视为第一个字符（0 是 UTF8 中的字符串结尾表示符），并返回一个空字符串，该字符串不同于 null。
将这三行替换为：
String dataString = Encoding.UTF8.GetString(e.Buffer, e.Offset, e.BytesTransferred);