Receiving on TCP

You can use either the TCP/IP listener, which is the inet daemon (INETD), or the WebSphere MQ listener.

Some Linux(R) distributions now use the extended inet daemon (XINETD) instead of the inet daemon. For information about how to use the extended inet daemon on a Linux system, see Using the extended inet daemon (XINETD).

Using the TCP/IP listener

To start channels on UNIX(R), the /etc/services file and the inetd.conf file must be edited, following the instructions below:

  1. Edit the /etc/services file:
    Note:
    To edit the /etc/services file, you must be logged in as a superuser or root. You can change this, but it must match the port number specified at the sending end.
    Add the following line to the file:
    MQSeries 1414/tcp
    where 1414 is the port number required by WebSphere MQ.
  2. Add a line in the inetd.conf file to call the program amqcrsta:
    MQSeries stream tcp nowait mqm /mqmtop/bin/amqcrsta amqcrsta
    [-m Queue_Man_Name]

The updates are active after inetd has reread the configuration files. To do this, issue the following commands from the root user ID:

When the listener program started by INETD inherits the locale from INETD, it is possible that the MQMDE will not be honored (merged) and will be placed on the queue as message data. To ensure that the MQMDE is honored, you must set the locale correctly. The locale set by INETD may not match that chosen for other locales used by WebSphere MQ processes. To set the locale:

  1. Create a shell script which sets the locale environment variables LANG, LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, and LC_MESSAGES to the locale used for other WebSphere MQ process.
  2. In the same shell script, call the listener program.
  3. Modify the inetd.conf file to call your shell script in place of the listener program.

It is possible to have more than one queue manager on the server machine. You must add a line to each of the two files, as above, for each of the queue managers. For example:

MQSeries1     1414/tcp
MQSeries2     1822/tcp

MQSeries2 stream tcp nowait mqm /mqmtop/bin/amqcrsta amqcrsta -m QM2

This avoids error messages being generated if there is a limitation on the number of outstanding connection requests queued at a single TCP port. For information about the number of outstanding connection requests, see Using the TCP listener backlog option.

Using the TCP listener backlog option

When receiving on TCP, a maximum number of outstanding connection requests is set. This can be considered a backlog of requests waiting on the TCP port for the listener to accept the request. The default listener backlog values are shown in Table 15.

Table 15. Default outstanding connection requests
Platform Default listener backlog value
AIX V4.2 or later 100
AIX V4.1 10
HP-UX 20
Solaris 100
Linux 100
All others 5

If the backlog reaches the values shown in Table 15, the TCP/IP connection is rejected and the channel will not be able to start.

For MCA channels, this results in the channel going into a RETRY state and retrying the connection at a later time.

For client connections, the client receives an MQRC_Q_MGR_NOT_AVAILABLE reason code from MQCONN and should retry the connection at a later time.

However, to avoid this error, you can add an entry in the qm.ini file:

TCP:
ListenerBacklog = n

This overrides the default maximum number of outstanding requests (see Table 15) for the TCP/IP listener.

Note:
Some operating systems support a larger value than the default. If necessary, this can be used to avoid reaching the connection limit.

To run the listener with the backlog option switched on, use the RUNMQLSR -B command. For information about the RUNMQLSR command, see the WebSphere MQ System Administration Guide book.

Using the WebSphere MQ listener

To run the listener supplied with WebSphere MQ, which starts new channels as threads, use the runmqlsr command. For example:

runmqlsr -t tcp [-m QMNAME] [-p 1822]

The square brackets indicate optional parameters; QMNAME is not required for the default queue manager, and the port number is not required if you are using the default (1414).

For the best performance, run the WebSphere MQ listener as a trusted application as described in Running channels and listeners as trusted applications. See the WebSphere MQ Application Programming Guide for information about trusted applications.

You can stop all WebSphere MQ listeners running on a queue manager that is inactive, using the command:

endmqlsr [-m QMNAME]

If you do not specify a queue manager name, the default queue manager is assumed.

Using the TCP/IP SO_KEEPALIVE option

If you want to use the SO_KEEPALIVE option (as discussed in Checking that the other end of the channel is still available) you must the add the following entry to your queue manager configuration file (qm.ini):

TCP:
   KeepAlive=yes

On some UNIX systems, you can define how long TCP waits before checking that the connection is still available, and how frequently it retries the connection if the first check fails. This is either a kernel tunable parameter, or can be entered at the command line. See the documentation for your UNIX system for more information.