为什么 UDPSocket.SendAsync() 需要 connect() 方法才能工作？

Question

当时我在 C# 中使用 XXXAsync 方法和 socketeventargs 在测试我的控制台应用程序时，数据没有被发送（在本地 - 在一台电脑内）并且在发件人应用程序中没有使用此代码抛出错误。

public class Client
{
    private static Socket FlashUDP = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
    private static IPEndPoint send_ipep = new IPEndPoint(IPAddress.Parse("192.168.100.41"), 14086);
    private static IPEndPoint rec_ipep = new IPEndPoint(IPAddress.Parse("192.168.100.41"), 14085);
    private static SocketAsyncEventArgs Sock_Args = new SocketAsyncEventArgs();
    private static SocketAsyncEventArgs Sock_Args2 = new SocketAsyncEventArgs();

private static byte[] dat1 = new byte[10];

//This function is called at main
private static void starter()
{
    Sock_Args.RemoteEndPoint = send_ipep;          
    Sock_Args.Completed += Sock_Args_Completed;
    string st = "ping";
    byte[] msg = Encoding.ASCII.GetBytes(st);
    Sock_Args.SetBuffer(msg, 0, 4);

   // FlashUDP.SendTo(msg, rec_ipep);
    try
    {            
        FlashUDP.Bind(rec_ipep);
       // FlashUDP.Connect(send_ipep);
        FlashUDP.SendAsync(Sock_Args);
    }
    catch (Exception e)
    {
        Console.WriteLine(e.ToString());
    }

    Console.WriteLine("Sending...");
}

private static void Sock_Args_Completed(object sender, SocketAsyncEventArgs e)
{
    Console.WriteLine("sent sucessfully ");
    Console.WriteLine("++++++++++++++++++++++++");
}

但是，当 try catch 块中的 connect() 代码未被注释时，此应用成功发送了数据。它也在

时发送了数据

FlashUDP.SendTo("dat1", send_ipep);

代替了

FlashUDP.SendAsync(Sock_Args);

我是不是遗漏了什么，或者这是 udp 的工作方式？如果

我原以为

"SentTo()"

无需连接即可工作

"SendAsync()"

也应该在没有连接的情况下工作。连接对客户端来说不是问题，但对服务器来说是个问题，因为它必须处理许多客户端。当我不绑定（）接收器时，不会发送数据。有什么解决办法吗？谢谢！

Answer 1

根据 SendTo documentation 这是预期的行为：

If you are using a connectionless protocol [addition by me: which UDP is], you do not need to establish a default remote host with the Connect method prior to calling SendTo. You only need to do this if you intend to call the Send method.

SendAsync documentation（SendAsync 是前面提到的 Send 的异步等价物）然后指出：

The SendAsync method will throw an exception if you do not first call Accept, AcceptAsync, BeginAcceptBeginConnect, Connect, or ConnectAsync.

如果您想要与 SendTo 相同的行为，您应该使用 SendToAsync:

If you are using a connectionless protocol, you do not need to establish a default remote host with the BeginConnect, Connect, or ConnectAsync method prior to calling SendToAsync. You only need to do this if you intend to call the BeginSend or SendAsync methods.

为什么 UDPSocket.SendAsync() 需要 connect() 方法才能工作？

Why does UDPSocket.SendAsync() requires connect() method to work?

.net

c#

sockets

sendasync