Explanation for setsockopt()

[Amith_2]

Hello.
I am experiencing a delay when i sent message with size of 2200 bytes from my server program on HP-11 to the client program which is running on windows dos box.
Everytime when a message of size 2200 bytes is sent there is a delay in receiving the next request from the client. I was using the following options for the socket ,
setsockopt(circuit,SOL_SOCKET,SO_KEEPALIVE,(char *)&one,sizeof(one));
when i changed it to
setsockopt(circuit,IPPROTO_TCP,TCP_NODELAY,(char *)&one,sizeof(one));
the program started working fine.
Could anyone please explain to me what is the difference in the above two setsockop() defenitions and what caused the dealy in the previous case.

[Steven E. Protter]

Shalom Amith,

http://www.informatik.uni-frankfurt.de/doc/man/hpux/getsockopt.2.html

http://devrsrc1.external.hp.com/STK/cgi-bin/display-manpage.cgi?manpage=setsockopt&section=2&manOSName=hpux&manOSVersion=11.00

http://devrsrc1.external.hp.com/STKS/cgi-bin/man2html?manpage=/usr/share/man/man2.Z/getsockopt.2

SEP

[Antonio Cardoso_1]

have a look at:
man setsockopt
man tcp

in fact, the second setsockopt() doesn't contradict first one, but just adds the TCP option that "causes small amounts of output to be sent immediately",
"If TCP_NODELAY is set, the system sends small amounts of output immediately rather than gathering them into a single packet after an acknowledgement is received."

antonio.

[Amith_2]

Hello Antonio,

Does it mean that i can set two options together like mentioned below for my socket??

setsockopt(circuit,SOL_SOCKET,SO_KEEPALIVE,(char *)&one,sizeof(one));
setsockopt(circuit,IPPROTO_TCP,TCP_NODELAY,(char *)&one,sizeof(one));

[rick jones]

99 times out of 10, if setting TCP_NODELAY increases the performance of an application, it suggests the application is doing something doubleplusungood like presenting "logically associated data" (aka message) to the transport in more than one send call. In such situations, the proper fix is to use writev() or sendmsg().

To fully see what is happening, please take and post a tusc system call trace and a tcpdump packet trace of your server program talking to the Windows client.