How to specify the number of bytes to send when using Socket.SendToAsync()?

Question

I have ported my UDP based protocol implementation from using the Socket.BeginXXX methods to the Socket.XXXAsync methods as they take the SocketAsyncEventArgs class which has Buffer, Offset and Count properties so a single large buffer can be segmented and used for each operation.

Unfortunately I have just found out setting:

mySocketAsyncEventArgs.SendPacketsSendSize

Is not used when sending datagrams using:

mySocket.SendToAsync(mySocketAsyncEventArgs);

Instead the whole segment in SocketAsyncEventArgs.Buffer from Offset for Count bytes is sent! And I cannot use Socket.SendPacketsElements because that is only for connected Sockets!

Often I will only have a few bytes to send, but sometimes a thousand.. If the whole point of these overloads was to increase efficiency - they are not helping!

Please tell me there is way to specify the number of bytes to send in SocketAsyncEventArgs.Buffer on each operation..

Answer 1

You can use the SetBuffer() overload where you do not have to pass a byte[] buffer - just adjust the existing index and count to be used - then after the operation set count back to it's original value:

mySocketAsyncEventArgs.SetBuffer(mySocketAsyncEventArgs.Offset, numOfBytesWritten);
mySocket.SendToAsync(mySocketAsyncEventArgs);
...
mySocketAsyncEventArgs.SetBuffer(mySocketAsyncEventArgs.Offset, originalBufferSize);

Answer 2

UDP Protocol will always send all data in one packet. you need to use TCP if you want to sent package sized that is not based on data.

Answer 3

Have you tried setting SendPacketsSendSize to 0xFFFFFFFF and using SendPacketsElement.EndOfPacket?. It sounds promising in the docs: http://msdn.microsoft.com/en-us/library/system.net.sockets.socketasynceventargs.sendpacketssendsize.aspx