What TCP message will be generated for an incoming SYN request for which is there no matching LISTENING port

The TCP message that will be generated for an incoming SYN request for which is there no matching LISTENING port is; “Connection Refused”.

Now, when the above situation happens, the server will listen on the specified port and give a response of SYN-ACK packet so that it c an acknowledge the “SYN”packet requested by the client application which will generate a reply with ACK packet response that will make the established connection to end.

Read more about TCP at; link

"Connection Refused"

Explanation:

This is the error message that is returned when the server is not listening on the correct port, or the server is offline.

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