slip - Serial Line IP

     slip pseudo-ip-device

     The slip  program  implements  an  Internet  network  connection  over  a
     bidirectional  8-bit transport, usually a serial line.  The protocol used
     for this connection is the Serial Line Internet Protocol, SLIP for short.

     The pseudo-ip-device argument names one of the /dev/psip* devices that is
     offered  by  the  Minix TCP/IP driver inet(8).  The slip program reads IP
     packets from standard input and writes them to the pseudo IP device,  and
     reads  packets  from  the  pseudo  IP  device and writes them to standard
     output.  A typical use is like this:

                  stty raw 115200
                  slip /dev/psip2 &
          } </dev/tty01 >/dev/tty01

     The SLIP protocol is just a very  simple  packet  framing  protocol.   It
     defines  two  characters  as  markers  on a byte stream to frame packets.
     SLIP does not implement any higher level addressing, error detection,  or
     compression.   Thanks  to  its simplicity it can be used under Minix, any
     other system would prefer to use the Point-to-Point protocol: PPP.

     The SLIP packet framing protocol as defined in RFC-1055 is as follows:

     -    Packets are delimited by an END character, octal 300.  END is  often
          send  at  the  start  of  a  packet  too  to  reset the logic of the
          receiver, so that random noise isn't added to  the  beginning  of  a

     -    An ESC character (octal 333) is  used  to  escape  any  END  or  ESC
          characters  that may occur in an IP packet.  END and ESC are changed
          to ESC 334 and ESC 335 in the data stream.  (Note that  END  doesn't
          occur  within the data stream at all by escaping it this way, making
          finding the framing END easier.)


     /dev/psip*     Pseudo-IP devices for use by slip.


     Under Minix slip forks in two to handle the two data streams in or out of
     the  serial line.  Under Minix-vmd it uses asynchronous I/O to handle the
     two streams within one program.

     Kees J. Bot <>