Lantronix MPS100 EPS Reference Manual - Page 75

Setting up the RTEL Named Pipe Daemon

Page 75 highlights

TCP/IP Host Setup Reverse Telnet (RTEL) 7.3.5 Setting up the RTEL Named Pipe Daemon The basic concept behind the RTELPD daemon is to allow a UNIX system to use its own output filter programs that provide special purpose post-processing and then write the data into a named pipe device. The RTELPD daemon will read the data from the pipe and send it out over the network to a terminal or print server port. Note: The output filter in this case is either provided by the host system or is custom software. It is not provided as part of the RTEL software package. The command line parameters will be verified when the RTELPD daemon is started. The daemon process will then wait for input to arrive on the pipe device. When input data is detected, a connection attempt will be made to the target terminal server port, and if it is successful, data will start moving through the path. If the specified service or port is currently busy, the daemon process will wait until the service or port is available and then try again to connect. To the process dumping data into the pipe device, this waiting looks like flow control. Eventually, the connection attempt should succeed, and the user data will flow through the path. When the user process closes the pipe device, the RTELPD daemon will detect the end-of-file, close the network connection, then restart the job cycle by waiting for input to arrive on the pipe. It is important to remember that data will only move in one direction through a pipe. That is, data will flow from the host to the printer, but not from the printer back to the host. Host application packages like NewsPrint should be configured as if they were talking to parallel attached devices to ensure that the software is not expecting a response from the printer. To install the RTELPD daemon process and create a named pipe, 1 Create the named pipe and set up the server_hosts file using the mkpipe script. The process is shown in Figure 7-17. This example does not actually set up a print queue. It simply creates the named pipe and puts an entry in the server_hosts file that says how to start up the RTELPD daemon process. 7-15

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TCP/IP Host Setup
Reverse Telnet (RTEL)
7-
15
7.3.5
Setting up the RTEL Named Pipe Daemon
The basic concept behind the RTELPD daemon is to allow a UNIX system to use its own output filter
programs that provide special purpose post-processing and then write the data into a named pipe device.
The RTELPD daemon will read the data from the pipe and send it out over the network to a terminal or print
server port.
Note:
The output filter in this case is either provided by the host system or is custom
software. It is not provided as part of the RTEL software package.
The command line parameters will be verified when the RTELPD daemon is started. The daemon process
will then wait for input to arrive on the pipe device. When input data is detected, a connection attempt will
be made to the target terminal server port, and if it is successful, data will start moving through the path.
If the specified service or port is currently busy, the daemon process will wait until the service or port is
available and then try again to connect. To the process dumping data into the pipe device, this waiting looks
like flow control. Eventually, the connection attempt should succeed, and the user data will flow through
the path. When the user process closes the pipe device, the RTELPD daemon will detect the end-of-file,
close the network connection, then restart the job cycle by waiting for input to arrive on the pipe.
It is important to remember that data will only move in one direction through a pipe. That is, data will flow
from the host to the printer, but not from the printer back to the host. Host application packages like
NewsPrint should be configured as if they were talking to parallel attached devices to ensure that the
software is not expecting a response from the printer.
To install the RTELPD daemon process and create a named pipe,
1
Create the named pipe and set up the server_hosts file using the mkpipe script. The process is shown
in Figure 7-17.
This example does not actually set up a print queue. It simply creates the named pipe and puts an entry
in the server_hosts file that says how to start up the RTELPD daemon process.