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Is there any term called  "Sending Port"?

pamboo asked
I have a client which sends a UDP packet to a server listening at a port say 2000... The client is not binded to any port...Just it uses the sendto Winsock API for sending the UDP packet...

Will the client EXE use a port for sending this packet?

If so, How the OS performs the selection of free port...And my main concern is "Is there any Winsock APIs which allows the user to decide the sending port"

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I think there must be a connection between the client and server.The client must have a port that it is using.Have you tried the command netstat -an to see what ports are being used?

It could be random, it could be fixed. Really depends on how the application was coded.

Was I often see (especially when communication has to be bidirectional even if connectionless) is the source and destination ports set to be the same.
Dear Pamboo,

The Client does not actually have any port at the Client level but when it actually contacts the Server, and if the server is foked or threaded then there is a child or thread created and the client request shall alloted a port greater than 1024.
the os allocates the free and the nrearest port  from 1024. and if the connection is not closed like say TCP connection is not closed it remains in the Established state and then the os shall allocate another Port.
You can also optionally control these through the Proc file system, in Linux or any Posix system.
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