Port numbers are arbitrary and have no connection to protocols, you can host web pages on port 110 for example.
Generally port numbers are reserved for specific uses like 25=smtp, 110=pop3, 80=http etc. see :
http://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers[
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To determine a protocol on a specific port number you need to do packet sniffing which is an advanced topic.