To send break signals from a UNIX machine to serial devices using the TCP server mode, do the following:

1. Establish a TCP connection with the TCP port 966 set as the command port.
   The command/data used to send break signals to serial devices must go through the TCP command port (966) and not the data port (950). For example, in the 16-port NPort 5610, the command ports are TCP 966 (1st serial port) to 981(16th serial port).
2. Use the following packet formats to control the break signal to the TCP command port of your serial device.
   • To start a break command:
     Send to the serial device: 2 bytes [0x21, 0x00]
     Response from the serial device: 3 bytes [0x21, 'O', 'K']
   • To stop the break command:
     Send to the serial device: 2 bytes [0x22, 0x00]
     Response from the serial device: 3 bytes [0x22, 'O', 'K']
   • Use the UNIX function sleep() to control the duration of the break signal.