Re: TCP interface problem

Rich,

You might be getting bit by when of the "features" of TCP/IP.

When useing the TCP protocol, the data you sent is guarenteed to arive
at the destination in the same order you sent it.

Unlike UDP which might not arive and/or might not arive in the same
order you send it.

But, the kicker is that the data might not arrive in the same SIZE
packets!

Eg:
You might send 1,000 bytes in one send.  Because you are using TCP, all
1,000 bytes will get there and byte 1 will be before byte 2, 2 before
3, etc.

BUT, it might not get there in one 1,000 byte "receive".

You might receive 256 bytes followed by 128 follded by 64, then 64,
then 512.  Total is 1,000 bytes, but if you are not prepared to
"reassembe" the packets, you are hosed.

This breaking up of information is not as severe when dealing with
local networks...but if you are going over the Internet (or a WAN) it
happens all the time.  This is not hard to program, but it needs to be
delt with or you will not have a reliable connection.

In your case, after you receive the "truncated" 536 bytes, do another
receive.  Is it the "missing" data?  If so, you are experiancing the
above.  If not, I (again) am out in left field.

There might (probably) is a configuration value to "fix" the above
"problem"...but, IMHO, you are just delaying the inevitable and have a
time bomb ticking.

Regards,
Bob Crothers

-----Original Message-----
From: Rich Duzenbury <rduz@aros.net>
To: midrange-l@midrange.com <midrange-l@midrange.com>
Date: Friday, August 06, 1999 8:01 PM
Subject: TCP interface problem


>Hello midrangers,
>
>I have a TCP socket interface giving me fits today.  We are trying to
move it from a V3R2 machine to a V4R3 machine with little success.
>
>Records longer than 536 appear to be truncated.  I notice that when I
check the TCP connection status on the new machine (Netstat, option 3),
it happens to report 'Maximum segment size: 536'.
>
>The old machine reports 'Maximum segment size: 1452'.
>
>How can I convince the new system to allow the larger segment size
(Assuming this is the real problem).
>
>This program does not appear to use any type of SETSOCKOPT calls, btw.
>
>Thank you.
>
>Regards,
>Rich
>
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