Connecting to ZY

Once the ZY is booted up and running, it sets up a listening TCP socket. To connect to this listening socket, the client program must make a TCP connection to host zyn (where n is the ZY number) at port 5240. The ZY will respond with a greeting, if the connection was successful. While the ZY and the client program are connected, the ZY will send a newline character to the client every 60 seconds to make sure that the client has not been disconnected. If it has, the ZY will close the connection and resume listening. The client program should therefore interpret a single newline character as a ``null'' command and do nothing. Note that it is possible to connect to the ZY with a standard telnet program, as in the following example for zy0 and the Sun OS telnet:

  (3) rcreager on bunda% telnet zy0 5241
  Trying 192.33.116.170...
  Connected to zy0.
  Escape character is '^]'.
  HELLO This is ZY0 ver. 2.30
  CONNECT 1, 5241, bullwinkle is connected to primary port
  23154   50947.78763632  STW 1, 0x00013007
  bye
  0       50947.78767148  BYE 1, 5241, Closing Connection
  Connection closed by foreign host.

This is useful for trouble-shooting purposes or to familiarize oneself with the command syntax of the ZY. Set the telnet program to local echo and send on end of line. Some telnet programs will correctly set themselves to this basic setup because the ZY program is not really a telnet server and therefore the telnet negotiation will fail.