多线程套接字服务器-接收数据

Question

I have a simple TCP server, which uses asynchronous sockets. The challenge I'm facing is this:

I have the following TCP server class:

 public class tcp_server {
         const int max_clients = 300;
         const int max_buffer_size = 10;

         public AsyncCallback pfnWorkerCallBack;
         private Socket m_mainSocket;
         private Socket[] m_workerSocket = new Socket[max_clients];
         private int m_clientCount = 0;

          ... 

         public void OnClientConnect(IAsyncResult asyn) { }
         public void WaitForData(System.Net.Sockets.Socket soc, int socket_id) { }
         public void OnDataReceived(IAsyncResult asyn)

         public class SocketPacket
         {
            public System.Net.Sockets.Socket m_currentSocket;
            public byte[] dataBuffer = new byte[max_buffer_size];
            public int socket_id = -1;
         }
}

Here's the full code for OnDataRecieved function:

    public void OnDataReceived(IAsyncResult asyn)
    {
        try
        {
            SocketPacket socketData = (SocketPacket)asyn.AsyncState; // cast

            int iRx = 0;
            iRx = socketData.m_currentSocket.EndReceive(asyn);

            char[] chars = new char[iRx + 1];
            System.Text.Decoder d = System.Text.Encoding.UTF8.GetDecoder();
            int charLen = d.GetChars(socketData.dataBuffer, 0, iRx, chars, 0);

            WaitForData(socketData.m_currentSocket, socketData.socket_id);
        }
        catch (ObjectDisposedException)
        {
            log("OnDataReceived: Socket has been closed\n");
        }
        catch (SocketException se)
        {
            log(se.Message);
        }
    }

max_buffer_size is set to 10. If I send 100 bytes to server, onDataRecieve will execute 10 times.

I have 3 problems:

1 I need to 'collect' all 100 bytes and then pass it to another function that will check for commands in the received data. Client adds 4 byte 'packet end identifier' at the end of the packet, because the data size is not always known beforehand. How/where can I define this temporary buffer, so onDataRecieve would fill it up, if end is found, pass the data to command identification function?

2 Client might send me a lot of data from different threads (on same connection). I need a way to have multiple temporary buffers for each packet received, so I can wait until they fill up and pass the buffer whichever gets filled up first to command identification function and then clear/remove the buffer.

For example:

1. Client (Thread/Packet #1)->Server (incomplete data, thread hangs for some reason)
2. Client (Thread/Packet #2)->Server (complete data, buffer gets passed to command id funct)
3. Client (Thread/Packet #1)->Server (the rest of the data for 1st packet arrive, buffer passed to command id func)

3 I need to be able to access this buffer from outside (public) so I can start using that buffer from another class while it's filling up.

I hope that makes sense. How can I accomplish this?

Answer 1

1. I believe that needs to either be in OnDataReceived or call off to another class via a delegate or reference to another class or interface. If you call to another class then the callback function should take in the bytes that were just received and process them. The important thing here is any necessary synchronization between threads which is why I think it needs to be executed from within OnDataReceived. Also I notice you are decoding characters during each call to OnDataReceived. That is probably best to do once you have a full packet, unless you are for sure only ever sending single-byte characters (ASCII), otherwise you might try to decode a character that has been split across sends.

2. Each thread in the client needs to have its own connection or needs to make sure it sends its whole packet at once within a proper lock. If each thread has its own connection, then you need a buffer per connection on the server. If you only have one connection on the client, then there is no need for multiple buffers on the server.

3. This is a good spot for a blocking queue. This is the CLR version: http://msdn.microsoft.com/en-us/library/dd267312.aspx . You would want to use it with Concurrent Queue, http://msdn.microsoft.com/en-us/library/dd267265.aspx . The tcp_server class would place the packet in the queue when it is fully received and then another thread(s) could be blocking on reading from the queue and process any packets that get placed on the queue.