COMTI with TCP/IP and MS Link Does Not Succeed If Less Data Is Returned Than Was Sent (313151)

SYMPTOMS

When you use COM Transaction Integrator (COMTI) and TCP/IP by means of MS Link, with a modified version of the Microsoft supplied child server sample program (Mscmtics.cbl), and if the data that is returned from the mainframe host program is fewer bytes than what was sent to the mainframe host program, you receive an error message that is similar to the following:

COMTI Event 102:
Runtime error 2159 : the tcp transport received a socket error while attempting to receive user data expected length 34, received length 25.
IP ADDRESS : (address) port number (port).
Trans ID : (trans ID)

CAUSE

This problem occurs when the child server program on the mainframe is designed to return fewer bytes of data than are received from COMTI.

The Microsoft-supplied Mscmtics.cbl child server sample program is designed to return at least as many bytes of data as are sent to the host, even if the COMTI type library is designed to expect fewer bytes of data to be returned. If the type library is designed to receive fewer bytes, the COMTI runtime ignores the additional bytes that are returned by the Mscmtics.cbl child server program.

For example, the error scenario occurs as follows:

The host expects to receive 34 bytes of data to process, for example, a first name, a last name, and an address.
The host takes that 34 bytes of information and goes to a database to get additional information to return.
The host returns only 25 bytes (for example, the phone number).
The modified version of the child server program sends only 25 bytes of data back to the COMTI runtime.

In this case, if COMTI receives only 25 bytes from the host, this error occurs because the COMTI runtime was designed to expect to receive at least as many bytes of data as it sent (34 bytes).

RESOLUTION

Microsoft SNA Server 4.0

For SNA Server 4.0, the product will not be changed to allow for returning less data than is sent to the host when using TCP/IP by means of MS Link.

Microsoft Host Integration Server 2000

To resolve this problem, obtain the latest service pack for Host Integration Server 2000. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:

328152 How to Obtain the Latest Host Integration Server 2000 Service Pack

STATUS

Microsoft has confirmed that this is a problem in Microsoft Host Integration Server 2000.

This problem was first corrected in Host Integration Server 2000 Service Pack 1.Microsoft has confirmed that this is a problem in Microsoft SNA Server Version 4.0.

MORE INFORMATION

A COMTI tracebits trace of a method call that sends 34 bytes to the mainframe and receives 25 bytes in return shows the TCP Transport Link exiting abnormally as follows:

Feb 15 17:19:07.296	18060	TCP Transport DistribLink is sending user 
data, length = 34
 Feb 15 17:19:07.296	18010	TCP Transport SendBuf entered, 34 bytes 
to send
 Feb 15 17:19:07.296	18130	TCP Transport SendBuf: Bytes sent=34.
 Feb 15 17:19:07.296	18011	TCP Transport SendBuf exited normally
 Feb 15 17:19:07.531	18016	TCP Transport ReceiveBuf entered, maximum 
34 bytes to receive
 Feb 15 17:19:07.531	18090	TCP Transport RecvBuf: Remaining=34, 
receive size=34.
 Feb 15 17:19:07.531	18092	TCP Transport RecvBuf: Bytes received=25, 
total received so far=25.
 Feb 15 17:19:07.531	18090	TCP Transport RecvBuf: Remaining=9, 
receive size=9.
 Feb 15 17:19:07.531	18091	TCP Transport RecvBuf: Shutdown occurred.
 Feb 15 17:19:07.531	18017	TCP Transport ReceiveBuf exited normally, 
25 bytes rcvd, Data Complete = 1
 Feb 15 17:19:07.531	18024	TCP Transport Link exited abnormally, 
HRESULT = 0000000b