10.2.4 LANSA Communications Extensions Listener Records (COMMS_LISTENER_RECS)
Configuration item COMMS_LISTENER_RECS allows the creation, change and deletion of LANSA Communications Extensions Listener Records. These records define the parameters used by the listener job when employing the listener record's communications method.
Select configuration item COMMS_LISTENER_RECS from the COMMS_EXTENSIONS group to review these records.
The screen presented looks something like this:
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This screen lists all the listener records stored in the LANSA Communications Extensions routing table.
Working from this screen you can, by entering one of the options beside a list entry, perform these actions:
2=Review/Change: Display the details for the listener record. From the screen displayed, press the Change function key to enable the fields to be amended.
4=Delete: Delete the listener record on which this option is entered.
Pressing the Add/Create function key will present the Add Communications Listener Record screen which allows the addition of a new listener record.
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These input options are required on the Add Listener Record screen:
Communications Method
Is the communications method used by the Listener. The communications methods supported on the IBM i by LANSA Communications Extensions are:
- SOCKET: Use TCP/IP sockets.
Number of Session Jobs to Prestart
Enter the number of session jobs to be prestarted by the listener job. Session jobs are prestarted to reduce the connection time from requesting clients by avoiding the time required by the operating system to start a job.
It must be a positive number in the range 1 to 9,999.
Note: The subsystem where the session jobs run (and the job queue where they are submitted to) must have a "maximum number of jobs active at the same time" value of at least the number entered in the "Number of Session Jobs to Prestart" field, otherwise some session jobs will stay on the job queue.
Connection Identifier
The meaning and purpose of this field is specific to each communications method:
- For SOCKET (TCP/IP) this is the port number at which the listener job will listen for connection requests. If left blank, the default value of 4545 is used. The workstations must be configured to connect to the port number nominated here. If left blank they will use the default value of 4545.
Cryptographic Algorithm
The cryptographic algorithm used to encrypt transmitted data:
- *NONE - No encryption. This is compatible with prior releases of LANSA Communication extension.
- SSL - Secure Sockets Layer. SSL and its successor TLS are today the most widely used protocols providing end-to-end encryption of network communications. LANSA's SSL implementation uses anonymous Diffie-Hellman keys generated anew for each session, used for symmetric encryption with SHA-1 based ciphers. It does not require certificates for server authentication.
- DES - Data Encryption Standard algorithm. This standard was adopted by ANSI in 1981. DES is a block cipher, it encrypts data in 64 bit blocks. The key length is 64 bits.
- TWF - Twofish cryptographic algorithm. This was one of the five finalists for the new encryption standard known as Advanced Encryption Standard(AES). This standard was introduced by NIST(National Institute of Standards and Technology). Twofish (copyright Counterpane Internet Security Inc.) is a 128 bit block cipher. The key length can be 128, 192 or 256 bits.
The default value is *NONE. That is, the data is not encrypted.
The use of encryption and/or compression algorithms cause more CPU cycles to be consumed during communication sessions. However this overhead is quite small when compared to other communication overheads found in most normal operational situations.
Note: If a cryptographic algorithm is selected, the listener job will only accept connection requests from clients that support the selected cryptographic algorithm.
If you have clients that are on an earlier version of LANSA Communications Extensions (versions 1.x) which doesn't support encryption, then you can only accept connection requests from them if you select *NONE.
Press the prompt key on this field to select from the list of valid cryptographic algorithms.
Cryptographic Algorithm Selection
From this panel, you can select a cryptographic algorithm by typing its name in the input field or by positioning the cursor on the required cryptographic algorithm and pressing the Enter/record advance key.
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Data Compression
Whether the transmitted data should be compressed or not:
- YES - Allow LANSA Communications Extensions to compress the data before it is transmitted. This is the default value.
- NO - Don't compress the data. You would normally choose this option only when enabling tracing for troubleshooting.
Login Timeout
How long to wait (in seconds) for the client's login packet before timing out (Enter a value from 1 to 32 seconds).
Enable IPv6
Whether to enable support for Internet Protocol version 6.
- YES – The listener accepts client connections using IPv6 in addition to IPv4.
- NO - The listener only accepts client connections using IPv4. This is the default value.
TCP_NODELAY TCP/IP Socket Option
Indicates whether the TCP_NODELAY TCP/IP socket option should be enabled or not. This option is displayed only if the communications method is SOCKET (TCP/IP). Valid values are:
- YES - Disable the Nagle algorithm to allow small data packets to be delivered to the remote system without delay. This is the default value.
- NO - Don't disable the Nagle algorithm.
- The Nagle algorithm coalesces a small data buffer from multiple send calls and delays sending it until an acknowledgement for the previous data packet sent is received from the remote system. It is enabled by default in TCP/IP sockets.
- As the LANSA Communications Extensions implements its own data buffering, the Nagle algorithm is not needed.
TCP_KEEPALIVE TCP/IP Socket Option
Select this option to enable the TCP/IP socket option .
An application can request a TCP/IP provider to enable the use of keep alive packets on TCP connections by turning on the TCP_KEEPALIVE socket option. If a connection is dropped, as the result of the KEEPALIVE option, the error code 10052 is returned to any calls in progress on the socket. Any subsequent calls will fail with error code 10057. Refer to Communications Error Codes in the for further details of these error codes.
Tracing Options
Check which events or actions require tracing when the listener job is running.
Refer to Tracing Options in the for the details of each option.
Logging Options
Enables the recording of normal events which need tracking when the listener job is running. On the IBM i messages are sent to the job's external message queue and will be listed in the job log.
Refer to 10.2.3 LANSA Communications Extensions Facility Tracing Records (COMMS_FACILITY_TRACE) for the details of each option.