Contents:
Part Two:
Setting
up svr_tty - Direct Connection for Remote Port
Use where the serial line is accessed via a network port on the Communications
Server (i.e., for use with svr_tty).
Using Web Configuration.
Invoke the Server's setup utility by entering its IP address in a network-connected
web-browser, (i.e. http://192.168.80.17).
When the Setup front page is displayed:
Step 1.
Press the 'Setup' button. Specify a valid user name and password,
if prompted.
Step 2.
Select the 'Direct Connection' hyperlink from the main Setup
screen.
Step 3.
Select 'Direct Connection' from the 'Setup Direct Connection'
screen.
Step 4.
Specify the following:
- Ports to which terminal(s) are to be connected - Port 01
to 08 or 16.
- Baud Rate - from 5 to 230,400 or autobaud (default 115,200).
- Character size - 8 or 7 (default 8).
- Parity - none, even, odd, mark or space (default none)
- Stop bits - 1 or 2 (default 1)
- Flow Control - none, hardware or software (default hardware)
Step 5.
Press the Configure button when ready. The input parameters
are implemented immediately. The setup program now confirms that the
input has been accepted by displaying the Configuration Results
screen.
Setting
up svr_tty - the Configuration File
As described above, a svr_tty daemon process must be used to make connection
between pseudo-ttys and Communications Server serial ports. This
mapping is defined in a configuration file. The configuration
file may contain one or more lines, each of which can be a:
- blank line; or
- comment (line starting with '#'); or
- port configuration entry
A port configuration entry consists of a single line with three fields
separated by white-space characters. These fields specify:
- a pseudo-tty device name;
- the IP address of an Communications Server unit (hostname or dotted notation);
- a TCP port number
The pseudo-tty device will be connected to the serial port specified
by the IP address (server name) and TCP port number (telnet listener).
The exact form of the master pseudo-tty device name varies depending
on the operating system, and whether tty cloning is available (see below
for more details).
Example configuration using psuedo-ttys::
#
# R&D lab printer
#
ptyq2 lab_ts 2001
#
# Support modems
#
ptyq3 192.168.80.17
2007
ptyq4 192.168.80.17
2008
The above configuration file uses psuedo-ttys, where the psuedo-tty
name refers to a master psuedo-tty device (i.e. ptyq2 refers to /dev/ptyq2).
This would connect pseudo-tty '/dev/ptyq2' to telnet listener 2001
on the 'lab_ts' EasyServer II. Likewise, '/dev/ptyq3' and '/dev/ptyq4'
would be connected to serial ports 7 and 8 on the EasyServer II identified
by the IP address 192.168.80.17.
Applications that wish to use the above serial ports should use
the corresponding slave psuedo-tty device. For example, the printer
interface script for the R&D lab printer above would send data to
/dev/ttyq2 (this being the slave end of /dev/ptyq2). See Setting
up a Remote Port Facility for a discussion on the theory of
operation for master / slave ttys.
When selected pseudo-tty devices to use in a configuration file, you
should pick ones which will not be in use when svr_tty is invoked.
If svr_tty is started at boot time, this is generally easy (none will
normally be allocated at this time). Don't use the same pseudo-tty
device in more than one configuration entry or more than one configuration
file.
To help avoid this problem, it is possible to use cloned psuedo-ttys.
Example configuration, using cloned psuedo-ttys:
#
# a few more printers
#
doc_printer 192.159.80.17
2005
hw_printer 192.159.80.17
2006
Instead of having to select appropriate psuedo-ttys, svr_ttys can create
its own links to the psuedo-ttys. svr_tty will establish these
links to the documentation and hardware printers (/dev/doc_printer and
/dev/hw_printer) by finding valid psuedo_ttys when invoked with the
'-n' switch (see Invoking
the Daemon).
Configuration files should be owned by root and should not be writable
by ordinary users, i.e. chmod 644. A single svr_tty daemon process
can handle many individual connections but for performance reasons we
recommend that the number is kept small. For slow or infrequently
used devices up to 16 devices per daemon should be fine. For fast
devices an upper limit of 4 devices is generally reasonable.
Multiple daemon processes can be used to handle large numbers of devices,
and the system overhead for each is small. On some systems you
may find that the operating system will not allocate enough file descriptors
to a process to allow more than 16 or so devices to be handled by a
single daemon.
Setting up
svr_tty - Invoking the Daemon
The svr_tty daemon can be invoked from a shell command-line (useful
for testing) or a system startup file. It should not be invoked
until after all TCP/IP initialisation has completed. It should
be invoked with superuser privileges, i.e. with an effective UID of
0.
svr_tty has the following command line options:
svr_tty [-?hvdofmnkBF][-t
poll-time[,wait-time]][-D debug-file]
[-p "link server port "][config-file]
where
- -h displays svr_tty help
- -? displays svr_tty help
- -d send debug to stderr
- -D debug-file sends debug to debug-file
- -v display svr-tty version number
- -o use old configuration format (psuedo-ttys)
- -n use new configuration format (links to psuedo-ttys)
- -f open network connection on first pty data
- -m close network connection on pty close (not supported on
all systems)
- -k use TCP keepalives
- -B run as daemon (default)
- -F run in foreground
- -t poll-time[,wait-time] check for network disconnect
poll-time = how often to check
wait-time = how long to wait
- -p "link server port" specify port configuration
link = device name to link
server = server name or IP address
port = TCP port number
The default configuration file is /etc/svr_tty.conf
Here are some example command lines:
svr_tty -D /tmp/svr_tty.log
will start svr_tty, using the old configuration format as read from
/etc/svr_tty.conf
Debug will be sent to /tmp/svr_tty.log
sr_tty -f -n /usr/local/svr_tty.conf
will start svr_tty, using the new configuration format as read from
the /usr/local/svr_tty.conf
TCP connections will be made the first time data is sent to any tty
listed in /usr/local/svr_tty.conf
Troubleshooting
If you have problems, first make sure that the svr_tty daemon is running.
The switches -F and -d can help by keeping svr_tty in the foreground
and displaying messages showing what it is doing. The most common
problem is that svr_tty refuses to connect to one or more telnet listeners.
This may occur because the telnet listener is not enabled or access
to the port is not configured as 'remote' or 'dynamic'.
The Communications Server has a number of commands that can be used
to check the configuration and status of telnet listeners and serial
ports, i.e.:
show telnet listener
all status
show telnet listener
all characteristics
show/monitor port <number>
characteristics
show/monitor port <number>
counters
Building or
Retrieving a Copy of svr_tty
The easiest way to get a binary copy of svr_tty for your favourite
operating system is via the Stallion WWW pages at http://www.stallion.com
Alternatively, you can find the binaries on our anonymous FTP site:
ftp://ftp.stallion.com, in the
directories drivers/easyserver2/.
If you do not have access to our site or we don't have a precompiled
binary for your operating system, you can compile svr_tty from the source
code. This is available from an EasyServer II unit itself. The
latest source code is always available via the Internet.
To extract the source code from a server, see the online tutorial
section 'Unix Utility Programs' or point a Web browser at the pages
built into the server and select 'Files'.
Compilation instructions for various operating systems are given in
the comments at the beginning of the svr_tty source code. For
other operating systems you may need to experiment using the documented
instructions as a guideline. Please contact the distributor from
whom you purchased the product if you require any further assistance.
The svr_tty binary is normally installed in /etc and should be executable
by the superuser.
