Editing UUCP (section)

====Initial handshake====
On starting, uucico will respond by sending an identification string, <code>\20Shere=''hostname''\0</code>, where \20 is the control-P character, and \0 is a trailing null. The caller's UUCP responds with <code>\20S''callername'' ''options''\0</code>, where ''options'' is a string containing zero or more Unix-like option switches. These can include packet and window sizes, the maximum supported file size, debugging options, and others.

Depending on the setup of the two systems, the call may end here. For instance, when the caller responds with their system name, the called system may optionally hang up if it does not recognize the caller, sending the <code>RYou are unknown to me\0</code> response string and then disconnecting.