Re: Reading data on Aysnchronous socket server
- From: "William Stacey [MVP]" <william.stacey@xxxxxxxxx>
- Date: Thu, 16 Feb 2006 17:17:00 -0500
You must always *expect you will get 1 or more bytes (or 0 if shutdown by
sender) upto max of Count bytes. That is all you can expect and you need to
design your logic always with that understanding. The sender may be sending
4 bytes (maybe a length) as one Send and then sending the data as the second
Send(). This could be because they wanted to save a buffer copy to join the
two arrays. On the other hand, that could make less efficient network
traffic if it means the first send/ack will always be only 4 bytes. So do
you pay the price in the buffer join(s) or slightly more traffic. Can't
really say as it depends on the app, net speed, etc.
--
William Stacey [MVP]
"Macca" <Macca@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:E40CE17A-1D77-48AF-A1B8-5027F939AE4A@xxxxxxxxxxxxxxxx
| Hi,
|
| I have a synchronous socket server which my app uses to read data from
| clients.
|
| To test this I have a simulated client that sends 100 byte packets.
|
| I have set up the socket server so that its buffer is bigger than this.
| I did this expecting the data to be read in one pass.
|
| However what I find is that on the first pass it only reads the first 4
| bytes and then on the second pass of begin.receive, reads the rest of the
| message. Is this usual?
|
| This happens each time I send my packet from the
| The code I have been using is the MSDN example( shown below).
|
| Can anyone tell me if it is possible to read the whole message sent form
the
| client on the first pass rather than it taking 2 or more passes?
|
| Thanks
| Macca
|
|
| using System;
| using System.Net;
| using System.Net.Sockets;
| using System.Text;
| using System.Threading;
|
| // State object for reading client data asynchronously
| public class StateObject {
| // Client socket.
| public Socket workSocket = null;
| // Size of receive buffer.
| public const int BufferSize = 100;
| // Receive buffer.
| public byte[] buffer = new byte[BufferSize];
| // Received data string.
| public StringBuilder sb = new StringBuilder();
| }
|
| public class AsynchronousSocketListener {
| // Thread signal.
| public static ManualResetEvent allDone = new ManualResetEvent(false);
|
| public AsynchronousSocketListener() {
| }
|
| public static void StartListening() {
| // Data buffer for incoming data.
| byte[] bytes = new Byte[1024];
|
| // Establish the local endpoint for the socket.
| // The DNS name of the computer
| // running the listener is "host.contoso.com".
| SN.IPHostEntry ipHostInfo = SN.Dns.GetHostEntry(hostname);
| SN.IPAddress ipAddress = ipHostInfo.AddressList[0];
| SN.IPEndPoint localEndPoint = new SN.IPEndPoint(ipAddress,
7777);
|
| // Create a TCP/IP socket.
| Socket listener = new Socket(AddressFamily.InterNetwork,
| SocketType.Stream, ProtocolType.Tcp );
|
| // Bind the socket to the local endpoint and listen for incoming
| connections.
| try {
| listener.Bind(localEndPoint);
| listener.Listen(100);
|
| while (true) {
| // Set the event to nonsignaled state.
| allDone.Reset();
|
| // Start an asynchronous socket to listen for connections.
| Console.WriteLine("Waiting for a connection...");
| listener.BeginAccept(
| new AsyncCallback(AcceptCallback),
| listener );
|
| // Wait until a connection is made before continuing.
| allDone.WaitOne();
| }
|
| } catch (Exception e) {
| Console.WriteLine(e.ToString());
| }
|
| Console.WriteLine("\nPress ENTER to continue...");
| Console.Read();
|
| }
|
| public static void AcceptCallback(IAsyncResult ar) {
| // Signal the main thread to continue.
| allDone.Set();
|
| // Get the socket that handles the client request.
| Socket listener = (Socket) ar.AsyncState;
| Socket handler = listener.EndAccept(ar);
|
| // Create the state object.
| StateObject state = new StateObject();
| state.workSocket = handler;
| handler.BeginReceive( state.buffer, 0, StateObject.BufferSize, 0,
| new AsyncCallback(ReadCallback), state);
| }
|
| public static void ReadCallback(IAsyncResult ar) {
| String content = String.Empty;
|
| // Retrieve the state object and the handler socket
| // from the asynchronous state object.
| StateObject state = (StateObject) ar.AsyncState;
| Socket handler = state.workSocket;
|
| // Read data from the client socket.
| int bytesRead = handler.EndReceive(ar);
|
| if (bytesRead > 0) {
| // There might be more data, so store the data received so
far.
| state.sb.Append(Encoding.ASCII.GetString(
| state.buffer,0,bytesRead));
|
| // Check for end-of-file tag. If it is not there, read
| // more data.
| content = state.sb.ToString();
| if (content.IndexOf("<EOF>") > -1) {
| // All the data has been read from the
| // client. Display it on the console.
| Console.WriteLine("Read {0} bytes from socket. \n Data :
{1}",
| content.Length, content );
| // Echo the data back to the client.
| Send(handler, content);
| } else {
| // Not all data received. Get more.
| handler.BeginReceive(state.buffer, 0,
| StateObject.BufferSize, 0,
| new AsyncCallback(ReadCallback), state);
| }
| }
| }
|
| private static void Send(Socket handler, String data) {
| // Convert the string data to byte data using ASCII encoding.
| byte[] byteData = Encoding.ASCII.GetBytes(data);
|
| // Begin sending the data to the remote device.
| handler.BeginSend(byteData, 0, byteData.Length, 0,
| new AsyncCallback(SendCallback), handler);
| }
|
| private static void SendCallback(IAsyncResult ar) {
| try {
| // Retrieve the socket from the state object.
| Socket handler = (Socket) ar.AsyncState;
|
| // Complete sending the data to the remote device.
| int bytesSent = handler.EndSend(ar);
| Console.WriteLine("Sent {0} bytes to client.", bytesSent);
|
| handler.Shutdown(SocketShutdown.Both);
| handler.Close();
|
| } catch (Exception e) {
| Console.WriteLine(e.ToString());
| }
| }
|
.
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