#unity/日常积累

# SocketAsyncEventArgs 类

-   参考

反馈

[](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0#definition)

## 定义

命名空间:

[System.Net.Sockets](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets?view=net-8.0)

程序集:

System.Net.Sockets.dll

Source:

[SocketAsyncEventArgs.cs](https://github.com/dotnet/runtime/blob/5535e31a712343a63f5d7d796cd874e563e5ac14/src/libraries/System.Net.Sockets/src/System/Net/Sockets/SocketAsyncEventArgs.cs)

表示异步套接字操作。

``` cs
public class SocketAsyncEventArgs : EventArgs, IDisposable
```

继承

[Object](https://learn.microsoft.com/zh-cn/dotnet/api/system.object?view=net-8.0)

[EventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.eventargs?view=net-8.0)

SocketAsyncEventArgs

实现

[IDisposable](https://learn.microsoft.com/zh-cn/dotnet/api/system.idisposable?view=net-8.0)

[](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0#examples)

## 示例

下面的代码示例为使用 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 类的套接字服务器实现连接逻辑。 接受连接后，从客户端读取的所有数据都发送回客户端。 继续读取并回显到客户端模式，直到客户端断开连接。 此示例使用的 BufferManager 类显示在 方法的代码示例 [SetBuffer(Byte[], Int32, Int32)](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs.setbuffer?view=net-8.0#system-net-sockets-socketasynceventargs-setbuffer(system-byte()-system-int32-system-int32)) 中。 此示例中使用的 SocketAsyncEventArgsPool 类显示在构造函数的代码示例 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs.-ctor?view=net-8.0) 中。

``` cs
// Implements the connection logic for the socket server.
// After accepting a connection, all data read from the client
// is sent back to the client. The read and echo back to the client pattern
// is continued until the client disconnects.
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;

    // Create an uninitialized server instance.
    // To start the server listening for connection requests
    // call the Init method followed by Start method
    //
    // <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);
    }

    // Initializes the server by preallocating reusable buffers and
    // context objects.  These objects do not need to be preallocated
    // or reused, but it is done this way to illustrate how the API can
    // easily be used to create reusable objects to increase server performance.
    //
    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);

            // 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);
        }
    }

    // Starts the server such that it is listening for
    // incoming connection requests.
    //
    // <param name="localEndPoint">The endpoint which the server will listening
    // for connection 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
        SocketAsyncEventArgs acceptEventArg = new SocketAsyncEventArgs();
        acceptEventArg.Completed += new EventHandler<SocketAsyncEventArgs>(AcceptEventArg_Completed);
        StartAccept(acceptEventArg);

        //Console.WriteLine("{0} connected sockets with one outstanding receive posted to each....press any key", m_outstandingReadCount);
        Console.WriteLine("Press any key to terminate the server process....");
        Console.ReadKey();
    }

    // Begins an operation to accept a connection request from the client
    //
    // <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)
    {
        // loop while the method completes synchronously
        bool willRaiseEvent = false;
        while (!willRaiseEvent)
        {
            m_maxNumberAcceptedClients.WaitOne();

            // socket must be cleared since the context object is being reused
            acceptEventArg.AcceptSocket = null;            
            willRaiseEvent = listenSocket.AcceptAsync(acceptEventArg);
            if (!willRaiseEvent)
            {
                ProcessAccept(acceptEventArg);
            }
        }
    }

    // This method is the callback method associated with Socket.AcceptAsync
    // operations and is invoked when an accept operation is complete
    //
    void AcceptEventArg_Completed(object sender, SocketAsyncEventArgs e)
    {
        ProcessAccept(e);
        
        // Accept the next connection request
        StartAccept(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();
        readEventArgs.UserToken = e.AcceptSocket;

        // As soon as the client is connected, post a receive to the connection
        bool willRaiseEvent = e.AcceptSocket.ReceiveAsync(readEventArgs);
        if (!willRaiseEvent)
        {
            ProcessReceive(readEventArgs);
        }
    }

    // This method is called whenever a receive or send operation is completed on a socket
    //
    // <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");
        }
    }

    // This method is invoked when an asynchronous 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.
    //
    private void ProcessReceive(SocketAsyncEventArgs e)
    {
        // check if the remote host closed the connection
        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);

            //echo the data received back to the client
            e.SetBuffer(e.Offset, e.BytesTransferred);
            Socket socket = (Socket)e.UserToken;
            bool willRaiseEvent = socket.SendAsync(e);
            if (!willRaiseEvent)
            {
                ProcessSend(e);
            }
        }
        else
        {
            CloseClientSocket(e);
        }
    }

    // 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
    //
    // <param name="e"></param>
    private void ProcessSend(SocketAsyncEventArgs e)
    {
        if (e.SocketError == SocketError.Success)
        {
            // done echoing data back to the client
            Socket socket = (Socket)e.UserToken;
            // read the next block of data send from the client
            bool willRaiseEvent = socket.ReceiveAsync(e);
            if (!willRaiseEvent)
            {
                ProcessReceive(e);
            }
        }
        else
        {
            CloseClientSocket(e);
        }
    }

    private void CloseClientSocket(SocketAsyncEventArgs e)
    {
        Socket socket = (Socket)e.UserToken;

        // close the socket associated with the client
        try
        {
            socket.Shutdown(SocketShutdown.Send);
        }
        // throws if client process has already closed
        catch (Exception) { }
        socket.Close();

        // decrement the counter keeping track of the total number of clients connected to the server
        Interlocked.Decrement(ref m_numConnectedSockets);

        // Free the SocketAsyncEventArg so they can be reused by another client
        m_readWritePool.Push(e);

        m_maxNumberAcceptedClients.Release();
        Console.WriteLine("A client has been disconnected from the server. There are {0} clients connected to the server", m_numConnectedSockets);
    }
}
```

## 注解

类 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 是 类的一组增强的一部分，这些增强 [System.Net.Sockets.Socket](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socket?view=net-8.0) 功能提供可由专用的高性能套接字应用程序使用的替代异步模式。 此类专为需要高性能的网络服务器应用程序而设计。 例如，当接收大量数据) 时，应用程序可以独占或仅在目标热区域使用增强型异步模式 (。

这些增强功能的主要功能是避免在大容量异步套接字 I/O 期间重复分配和同步对象。 类当前实现的 [System.Net.Sockets.Socket](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socket?view=net-8.0) Begin/End 设计模式要求为每个异步套接字操作分配对象 [System.IAsyncResult](https://learn.microsoft.com/zh-cn/dotnet/api/system.iasyncresult?view=net-8.0) 。

在新的 [System.Net.Sockets.Socket](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socket?view=net-8.0) 类增强中，异步套接字操作由应用程序分配和维护的可重用 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 对象描述。 高性能套接字应用程序非常清楚必须维持的重叠套接字操作的数量。 该应用程序可创建所需的 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 对象数量。 例如，如果服务器应用程序需要随时有 15 个未完成的套接字接受操作以支持传入客户端连接速率，则它可以为此分配 15 个可重用 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 对象。

使用此类执行异步套接字操作的模式包括以下步骤：

1.  分配一个新的 [SocketAsyncEventArgs](https://learn.microsoft.com/zh-cn/dotnet/api/system.net.sockets.socketasynceventargs?view=net-8.0) 上下文对象，或从应用程序池中获取一个空闲对象。
    
2.  将上下文对象的属性设置为即将 (完成回调方法执行的操作、数据缓冲区、缓冲区中的偏移量以及要传输的最大数据量，例如) 。
    
3.  调用适当的套接字方法 (xxxAsync) 以启动异步操作。
    
4.  如果异步套接字方法 (xxxAsync) 返回 true，请在回调中查询完成状态的上下文属性。
    
5.  如果异步套接字方法 (xxxAsync) 返回 false，则操作同步完成。 可查询上下文属性获取操作结果。
    
6.  重新使用上下文进行另一项操作，将其放回池中，或放弃它。
    

新的异步套接字操作上下文对象的生存期由应用程序代码和异步 I/O 引用的引用决定。 作为参数提交给异步套接字操作方法之一后，应用程序不必保留对异步套接字操作上下文对象的引用。 完成回调返回之前，应用程序会继续引用它。 但是，应用程序最好保留对上下文的引用，以便将来的异步套接字操作可以重复使用该引用。