使用NetworkStream将数据发送到服务器

Question

My assignment is to make a client that sends a ToString-override method to the server. My teacher sent me a Centralcomputer.exe which is the serverprogram, this program can recieve single strings and uses my local IP.

I connect without a problem, the problem comes when trying to execute this line Int32 bytesRead = stream.Read(bytesToRead, 0, klient.ReceiveBufferSize); my client freezes and the value of bytesRead is 0.

EDIT: Forgot to mention that the serverprogram responds with some "oriental" letters before client freezes.

 TcpClient client = new TcpClient();

 public async Task Connecting()
    {
        try
        {

            await client.ConnectAsync("127.0.0.1", 12345);

        }
        catch (ArgumentNullException e)
        {
            MessageBox.Show("ArgumentNullException: {0}" + e);
        }
        catch (SocketException e)
        {
            MessageBox.Show("SocketException: {0}" + e);
        }


  public void Sending()
    {
        string sendToServer = "Testing testing";
        byte[] data = System.Text.Encoding.ASCII.GetBytes(sendToServer);

        NetworkStream stream = client.GetStream();

        stream.Write(data, 0, data.Length);

        byte[] bytesToRead = new byte[client.ReceiveBufferSize];

        Int32 bytesRead = stream.Read(bytesToRead, 0, client.ReceiveBufferSize);    
        //This is where the client freezes

        MessageBox.Show("Received : " + Encoding.ASCII.GetString(bytesToRead, 0, bytesRead));
    }

I've never done this type of coding before so I really would appreciate some help just to get started!

Answer 1

There are only two scenarios when you will receive zero here:

• a zero-length read with a zero-length buffer can be used to detect when data becomes available
• the inbound socket has been closed

Assuming you didn't request a zero-length read, we can therefore assume the second option, and the socket closed. So: why did it close? Most likely, because the server gave up waiting for a message to reply to. Which suggests that it doesn't think you sent a complete message.

That in turn means one of:

• whatever you sent was not complete by the protocol's definition as expected by the server
• the data is still buffered and didn't send

To rule out the second, make sure you call Flush() after the Write . If that still doesn't fix it: check the protocol very carefully to see what you were meant to send. Maybe you missed a trailing linefeed or similar.

As a side note: any time you're doing a single Read on a socket, you've probably made a mistake. TCP isn't message oriented - it is just a stream. This means you always need a read-loop that handles whatever framing protocol is in use.

Answer 2

It is possible that your server expects a carriage return or/and a line feed before writing something back to the client.

Try to change the following line

string sendToServer = "Testing testing";

into

string sendToServer = "Testing testing \r\n";

Since we do not have access to the server's code, there is pretty hard to give you an exact solution.