Services 11.. PPoorrtt If you assume that the computer system name is like a street name, then a port number is like a street number. Usually, the port is a well-known number associated with a particular service. 22.. PPrroottooccooll Protocol specifies the way in which the service can be reached and how the communication between the client and the server is done. This is usually _t_c_p for connections and _u_d_p for messages. 33.. AAlliiaasseess ffoorr sseerrvviiccee The service may be known by other names. These are specified here.