The code that defines a protocol for execution. On a command line, the first characters are the protocol prefix. For example, to activate the File Transfer Protocol, the command line would look something like: ftp 192.168.100.102. This activates the FTP server in the machine with the 192.168.100.102 IP address. Following are common protocol prefixes:
Prefix Protocol
FTP File Transfer Protocol
SMB Server Message Block
SSH Secure Shell