问题
I've pulled from several examples to setup a Full Duplex C# TCP Client connected to a server. The basic concept is that the client and server both send/receive messages (commands and events). Therefore, I've developed a FullDuplexSocket class that exposes a Send method to send messages to the server and a event handler to receive messages from the server. Everything works except I can't seem to flush the buffer of messages received from the server. Each time the server sends a new message, the buffer in my socket contains all the old messages (already read) and the new message(s). I could split the messages by a known delimiter (/r/n) and keep track of them, but this will likely be the source of memory issues on long running communications. [Edit: Updated the code to a solution that no longer has buffer issues and works correctly].
Does anyone have any suggestions. Total rewrite??? Code is below in hope that it will help others.
Here's the FullDuplexSocket class:
using System;
using System.Text;
using System.Net.Sockets;
namespace Utilities
{
public class StateObject{
public Socket workSocket = null;
public const int BUFFER_SIZE = 1024;
public byte[] buffer = new byte[BUFFER_SIZE];
}
public class FullDuplexSocket : IDisposable
{
public event NewMessageHandler OnMessageReceived;
public delegate void NewMessageHandler(string Message);
public event DisconnectHandler OnDisconnect;
public delegate void DisconnectHandler(string Reason);
private Socket _socket;
private bool _useASCII = true;
private string _remoteServerIp = "";
private int _port = 0;
/// <summary>
/// Constructer of a full duplex client socket. The consumer should immedately define
/// and event handler for the OnMessageReceived event after construction has completed.
/// </summary>
/// <param name="RemoteServerIp">The remote Ip address of the server.</param>
/// <param name="Port">The port that will used to transfer/receive messages to/from the remote IP.</param>
/// <param name="UseASCII">The character type to encode/decode messages. Defaulted to use ASCII, but setting the value to false will encode/decode messages in UNICODE.</param>
public FullDuplexSocket(string RemoteServerIp, int Port, bool UseASCII = true)
{
_useASCII = UseASCII;
_remoteServerIp = RemoteServerIp;
_port = Port;
try //to create the socket and connect
{
_socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
_socket.Connect(RemoteServerIp, _port);
}
catch (Exception e)
{
throw new Exception("Unable to connect to the remote Ip.", e);
}
try //to listen to the socket
{
StateObject stateObject = new StateObject();
stateObject.workSocket = _socket;
_socket.BeginReceive
(
stateObject.buffer, //Buffer to load in our state object
0, //Start at the first position in the byte array
StateObject.BUFFER_SIZE, //only load up to the max per read
0, //Set socket flags here if necessary
new AsyncCallback(ReadFromSocket), //Who to call when data arrives
stateObject //state object to use when data arrives
);
}
catch (Exception e)
{
throw new Exception("Unable to start listening to the socket.", e);
}
}
/// <summary>
/// This will read the bytes from the socket, convert the bytes to a string and fire the OnMessageReceived event.
/// If the socket is forcibly closed, the OnDisconnect event will be fired. This happens when the other side of
/// the socket connection on the remote Ip is no longer available.
/// </summary>
/// <param name="asyncResult"></param>
public void ReadFromSocket(IAsyncResult asyncResult)
{
StateObject stateObject = (StateObject)asyncResult.AsyncState; //pull out the state object
int bytesReceived = 0;
try //to receive the message.
{
bytesReceived = stateObject.workSocket.EndReceive(asyncResult);
}
catch (Exception e) //Exception will occur if connection was forcibly closed.
{
RaiseOnDisconnect(e.Message);
return;
}
if (bytesReceived > 0)
{
RaiseOnMessageReceived
(
_useASCII ?
Encoding.ASCII.GetString(stateObject.buffer, 0, bytesReceived) :
Encoding.Unicode.GetString(stateObject.buffer, 0, bytesReceived)
);
stateObject.workSocket.BeginReceive
(
stateObject.buffer, //Buffer to load in our state object
0, //Start at the first position in the byte array
StateObject.BUFFER_SIZE, //only load up to the max per read
0, //Set socket flags here if necessary
new AsyncCallback(ReadFromSocket), //Who to call when data arrives
stateObject //state object to use when data arrives
);
}
else
{
stateObject.workSocket.Close();
RaiseOnDisconnect("Socket closed normally.");
return;
}
}
/// <summary>
/// Broadcast a message to the IP/Port. Consumer should handle any exceptions thrown by the socket.
/// </summary>
/// <param name="Message">The message to be sent will be encoded using the character set defined during construction.</param>
public void Send(string Message)
{
//all messages are terminated with /r/n
Message += Environment.NewLine;
byte[] bytesToSend = _useASCII ?
Encoding.ASCII.GetBytes(Message) :
Encoding.Unicode.GetBytes(Message);
int bytesSent = _socket.Send(bytesToSend);
}
/// <summary>
/// Clean up the socket.
/// </summary>
void IDisposable.Dispose()
{
try
{
_socket.Close();
RaiseOnDisconnect("Socket closed via Dispose method.");
}
catch { }
try
{
_socket.Dispose();
}
catch { }
}
/// <summary>
/// This method will gracefully raise any delegated events if they exist.
/// </summary>
/// <param name="Message"></param>
private void RaiseOnMessageReceived(string Message)
{
try //to raise delegates
{
OnMessageReceived(Message);
}
catch { } //when none exist ignore the Object Reference Error
}
/// <summary>
/// This method will gracefully raise any delegated events if they exist.
/// </summary>
/// <param name="Message"></param>
private void RaiseOnDisconnect(string Message)
{
try //to raise delegates
{
OnDisconnect(Message);
}
catch { } //when none exist ignore the Object Reference Error
}
}
}
The consumer of the class would simply do the following:
using System;
namespace Utilities
{
public class SocketConsumer
{
private FullDuplexSocket _fds;
public Consumer()
{
_fds = new FullDuplexSocket("192.168.1.103", 4555);
_fds.OnMessageReceived += fds_OnMessageReceived;
_fds.Send("Hello World!");
}
void fds_OnMessageReceived(string Message)
{
Console.WriteLine("Message: {0}", Message);
}
}
}
Any help would be great. Thanks!
回答1:
You're calling OnMessageReceived even if the buffer has not been filled (in case bytesRead < count). Consider switching to await for the async part of the application. That gets rid of the hideous callback recursion.
来源：https://stackoverflow.com/questions/19454634/how-do-i-flush-a-tcp-client-buffer