/// <summary>
/// Called when a message has been successfully sent.
///
/// Decodes the unsent bytes and tries sending them again.
/// </summary>
private void MessageSent(IAsyncResult result)
{
// Protect SendQueue
lock (SendQueue)
{
try
{
// Find out how many bytes were actually sent
int bytes = socket.EndSend(result);
// Get the bytes that we attempted to send
byte[] outgoingBuffer = (byte[])result.AsyncState;
// If no bytes were received, close the socket.
//if (bytes == 0)
//{
// //what to do here???
// socket.Close();
//}
// Prepend the unsent bytes and try sending again.
//else
{
outgoing = encoding.GetString(outgoingBuffer, bytes,
outgoingBuffer.Length - bytes) + outgoing;
SendBytes();
}
}
catch (Exception e)
{
SendRequest sr2 = SendQueue.Dequeue();
ThreadPool.QueueUserWorkItem(x => sr2.sendCallback(e, sr2.payload));
}
}
}
/// <summary>
/// We can write a string to a StringSocket ss by doing
///
/// ss.BeginSend("Hello world", callback, payload);
///
/// where callback is a SendCallback (see below) and payload is an arbitrary object.
/// This is a non-blocking, asynchronous operation. When the StringSocket has
/// successfully written the string to the underlying Socket, or failed in the
/// attempt, it invokes the callback. The parameters to the callback are a
/// (possibly null) Exception and the payload. If the Exception is non-null, it is
/// the Exception that caused the send attempt to fail.
///
/// This method is non-blocking. This means that it does not wait until the string
/// has been sent before returning. Instead, it arranges for the string to be sent
/// and then returns. When the send is completed (at some time in the future), the
/// callback is called on another thread.
///
/// This method is thread safe. This means that multiple threads can call BeginSend
/// on a shared socket without worrying around synchronization. The implementation of
/// BeginSend must take care of synchronization instead. On a given StringSocket, each
/// string arriving via a BeginSend method call must be sent (in its entirety) before
/// a later arriving string can be sent.
/// </summary>
public void BeginSend(String s, SendCallback callback, object payload)
{
SendRequest sendRequest = new SendRequest(s, callback, payload);
SendQueue.Enqueue(sendRequest);
SendMessage(SendQueue.Peek());
SendRequest currnetSR = SendQueue.Dequeue();
lock (sendSync)
{
ThreadPool.QueueUserWorkItem(x => currnetSR.sendCallBack(null, currnetSR.payload));
}
}
/// <summary>
/// Checks if the entire message has been sent. If the message hasn't been sent
/// or there is another request, begin sending it.
/// </summary>
private void SendBytes()
{
if (SendQueue.Count > 0)
{
// If the entire message has been sent.
if (outgoing == "")
{
// Dequeue the send request.
SendRequest sr = SendQueue.Dequeue();
// Call the appropriate callback.
ThreadPool.QueueUserWorkItem(x => sr.sendCallback(null, sr.payload));
// If there's another request in the queue, get its message and begin sending it.
if (SendQueue.Count > 0)
{
outgoing = SendQueue.Peek().message;
byte[] outgoingBuffer = encoding.GetBytes(outgoing);
outgoing = "";
try
{
socket.BeginSend(outgoingBuffer, 0, outgoingBuffer.Length,
SocketFlags.None, MessageSent, outgoingBuffer);
}
catch (Exception e)
{
SendRequest sr1 = SendQueue.Dequeue();
ThreadPool.QueueUserWorkItem(x => sr1.sendCallback(e, sr1.payload));
}
}
}
// Otherwise, the entire message has not been sent. Send more.
else
{
byte[] outgoingBuffer = encoding.GetBytes(outgoing);
outgoing = "";
try
{
socket.BeginSend(outgoingBuffer, 0, outgoingBuffer.Length,
SocketFlags.None, MessageSent, outgoingBuffer);
}
catch (Exception e)
{
SendRequest sr2 = SendQueue.Dequeue();
ThreadPool.QueueUserWorkItem(x => sr2.sendCallback(e, sr2.payload));
}
}
}
}
/// <summary>
/// This should be called only after a lock on sendRequests has been acquired.
/// It pings back and forth with the BytesSent callback to send out all the strings in
/// the queue. This method gets the string at the front of the queue and attempts
/// to send it. BytesSent takes care of making sure all of the bytes are actually sent
/// before calling this method again to send the next string.
/// </summary>
private void ProcessSendQueue()
{
while (sendRequests.Count > 0)
{
sendBytes = encoding.GetBytes(sendRequests.First().Text);
try
{
socket.BeginSend(sendBytes, sendCount = 0, sendBytes.Length, SocketFlags.None, BytesSent, null);
break;
}
catch (Exception e)
{
SendRequest req = sendRequests.Dequeue();
ThreadPool.QueueUserWorkItem(x => req.Callback(e, req.Payload));
}
}
}
/// <summary>
/// Sends a string to the client
/// </summary>
private void SendMessage(SendRequest sr)
{
// Get exclusive access to send mechanism
lock (sendSync)
{
String message = sr.message;
// Append the message to the unsent string
outgoing += message;
// If there's not a send ongoing, start one.
if (!sendIsOngoing)
{
sendIsOngoing = true;
SendBytes();
}
}
}
/// <summary>
/// This helper method sends out all the strings in the queue by calling
/// the BytesSent callback again and again. It tries to send the string at the
/// front of queue. It contains a call to another helper method BytesSent
/// to ensure all the bytes from the front string are sent before calling this
/// method again to send the next string.
///
/// IMPLEMENTATION NOTE: Should be called from within a lock for thread-safety.
/// </summary>
private void HandleSendQueue()
{
while (sendQueue.Count > 0)
{
sendBytes = encoding.GetBytes(sendQueue.First <SendRequest>().Text);
try
{
socket.BeginSend(sendBytes, sendCount = 0, sendBytes.Length,
SocketFlags.None, new AsyncCallback(BytesSent), (object)null);
break;
}
catch (Exception ex)
{
SendRequest request = sendQueue.Dequeue();
ThreadPool.QueueUserWorkItem((WaitCallback)(x => request.SendBack(ex, request.Payload)));
}
}
}
/// <summary>
/// This method is the callback used when bytes are being sent. It makes sure that all of
/// the bytes have been sent, then calls the appropriate callback and calls ProcessSendQueue.
/// </summary>
private void BytesSent(IAsyncResult ar)
{
try
{
// Compute how many bytes have been sent so far
sendCount += socket.EndSend(ar);
}
catch (Exception e)
{
SendRequest req = sendRequests.Dequeue();
ThreadPool.QueueUserWorkItem(x => req.Callback(e, req.Payload));
ProcessSendQueue();
return;
}
// If all the bytes were sent, remove the request from the queue, notify the
// callback, and process the next entry in the send queue.
if (sendCount == sendBytes.Length)
{
lock (sendRequests)
{
SendRequest req = sendRequests.Dequeue();
ThreadPool.QueueUserWorkItem(x => req.Callback(null, req.Payload));
ProcessSendQueue();
}
}
// If all the bytes weren't sent, send the rest.
else
{
try
{
socket.BeginSend(sendBytes, sendCount, sendBytes.Length - sendCount, SocketFlags.None, BytesSent, null);
}
catch (Exception e)
{
SendRequest req = sendRequests.Dequeue();
ThreadPool.QueueUserWorkItem(x => req.Callback(e, req.Payload));
ProcessSendQueue();
}
}
}
/// <summary>
/// We can write a string to a StringSocket ss by doing
///
/// ss.BeginSend("Hello world", callback, payload);
///
/// where callback is a SendCallback (see below) and payload is an arbitrary object.
/// This is a non-blocking, asynchronous operation. When the StringSocket has
/// successfully written the string to the underlying Socket, or failed in the
/// attempt, it invokes the callback. The parameters to the callback are a
/// (possibly null) Exception and the payload. If the Exception is non-null, it is
/// the Exception that caused the send attempt to fail.
///
/// This method is non-blocking. This means that it does not wait until the string
/// has been sent before returning. Instead, it arranges for the string to be sent
/// and then returns. When the send is completed (at some time in the future), the
/// callback is called on another thread.
///
/// This method is thread safe. This means that multiple threads can call BeginSend
/// on a shared socket without worrying around synchronization. The implementation of
/// BeginSend must take care of synchronization instead. On a given StringSocket, each
/// string arriving via a BeginSend method call must be sent (in its entirety) before
/// a later arriving string can be sent.
/// </summary>
public void BeginSend(String s, SendCallback callback, object payload)
{
// Protect SendQueue
lock (SendQueue)
{
// Create and store the send request.
SendRequest sendRequest = new SendRequest(s, callback, payload);
SendQueue.Enqueue(sendRequest);
// If there's not a send ongoing, start one.
if (SendQueue.Count() == 1)
{
// Append the message to the unsent string
outgoing += s;
SendBytes();
}
}
}
/// <summary>
/// The callback method used when sending bytes. It makes sure that all of the bytes
/// are sent before making the approriate callback and call to HandleSendQueue.
///
/// IMPLEMENTATION NOTE: Should be called from within a lock for thread-safety.
/// </summary>
/// <param name="arg">Object containing status of asyn operation</param>
private void BytesSent(IAsyncResult arg)
{
try
{
sendCount = sendCount + socket.EndSend(arg);
}
catch (Exception ex)
{
SendRequest request = sendQueue.Dequeue();
ThreadPool.QueueUserWorkItem((WaitCallback)(x => request.SendBack(ex, request.Payload)));
HandleSendQueue();
return;
}
if (sendCount == sendBytes.Length)
{
lock (sendQueue)
{
SendRequest req = sendQueue.Dequeue();
ThreadPool.QueueUserWorkItem((WaitCallback)(x => req.SendBack((Exception)null, req.Payload)));
HandleSendQueue();
}
}
else
{
try
{
socket.BeginSend(sendBytes, sendCount, sendBytes.Length - sendCount,
SocketFlags.None, new AsyncCallback(BytesSent), (object)null);
}
catch (Exception ex)
{
SendRequest request = sendQueue.Dequeue();
ThreadPool.QueueUserWorkItem((WaitCallback)(x => request.SendBack(ex, request.Payload)));
HandleSendQueue();
}
}
}
