The base process of MTR uses the Internet Control Message Protocol (ICMP), which is a Network Layer protocol (Layer 3) and doesn’t include the concept of ports. However, it is possible to force MTR to use UDP with the command MTR -u. In this case, the tests start with a transmission to port 33000 and increase the port number with each successive test. It is also possible to force MTR to use TCP, in which case you specify the port number to use with MTR -P -T.