TN3270 Server Keeps SNA Session Open When TN3270 Client is Restarted (183786)

RESOLUTION

The TN3270 Service sets the SO_KEEPALIVE socket option, so it's possible to tune the following Windows NT TCP/IP values to control the time interval before the TN3270 Server is notified of a client outage. Tuning this parameter will affect Windows NT TCP/IP keepalive behavior for all TCP/IP socket applications that set the SO_KEEPALIVE socket option.

WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys And Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT, you should also update your Emergency Repair Disk (ERD).

To change these parameters, perform the following procedure:

1. Start Registry Editor (REGEDT32.EXE), and to the following subkey:

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
   					

2. Add a value to the key described in the appropriate entry below, by Add Value from the Edit menu, typing in the value, and using the "Data Type" check box to set the value type.
3. Click OK.
4. Quit Registry Editor and restart the system for the changes to take effect.

All of the TCP/IP parameters are registry values located under one of two different subkeys of HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services:

• Tcpip\Parameters
• <Adapter Name>\Parameters\Tcpip

where <Adapter Name> refers to the subkey for a network adapter that TCP/IP is bound to, such as Lance01. Values under the latter key(s) are specific to each adapter. Parameters for which there may be both a DHCP and statically-configured value may or may not exist depending on whether the system/adapter is DHCP configured and/or static override values have been specified. A restart of the system is required for a change in any of these parameters to take effect.

KeepAliveTime
   Key: Tcpip\Parameters
   Value Type: REG_DWORD - Time in milliseconds
   Valid Range: 1 - 0xFFFFFFFF
   Default: 7,200,000 (two hours)
   Description: The parameter controls how often TCP attempts to verify
   that an idle connection is still intact by sending a keep alive packet.
   If the remote system is still reachable and functioning, it will
   acknowledge the keep alive transmission. Keep alive packets are not sent
   by default. This feature may be enabled on a connection by an
   application.
				

NOTE: The following KeepAliveInterval does not need to be changed, though it is provided below for reference purposes.

KeepAliveInterval
   Key: Tcpip\Parameters
   Value Type: REG_DWORD - Time in milliseconds
   Valid Range: 1 - 0xFFFFFFFF
   Default: 1000 (one second)
   Description: This parameter determines the interval separating keep
   alive retransmissions until a response is received. After a response is
   received, the delay until the next keep alive transmission is again
   controlled by the value of KeepAliveTime. The connection will be aborted
   after the number of retransmissions specified by
   TcpMaxDataRetransmissions has gone unanswered.