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ping' uses ICMP, specifically ICMP echo request and ICMP echo reply packets. There is no 'port' associated with ICMP. Ports are associated with the two IP transport layer protocols, TCP and UDP. ICMP packets are identified by the 'protocol' field in the IP datagram header. ICMP does not use either UDP or TCP communications services, it uses raw IP communications services. This means that the ICMP message is carried directly in an IP datagram data field. ('raw' comes from how this is implemented in software, to create and send an ICMP message, one opens a 'raw' socket, builds a buffer containing the ICMP message, and then writes the buffer containing the message to the raw socket.) The IP protocol value for ICMP is 1. (The protocol field is part of the IP header and identifies what is in the data portion of the IP datagram.)

The ICMP protocol has many different uses and capabilities. The ICMP message (contained in the IP datagram data field) has a 'type' field and a 'code' field to identify the different ICMP messages. For example, an ICMP

echo request message has type = 8 and code = 0 -- an ICMP echo reply has type = 0 and code = 0. There are other fields according to the type of ICMP message.

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