joshua@athertn.Atherton.COM (Sleaze Hack) (12/09/88)
I'm having trouble sending large blocks of data through a TCP socket.
When I use this code:
size = 16 * 1024 ;
stat = write(tcp_sock, buffer, size)
Bad things happen. Depending on the exact value of size, I get a stat
of -1, or the write just freezes, or the data sent gets zero'ed. If
size is set to 2K or less everything works fine. I'm using a Sun 3/140
with SunOS 3.4, but the solution to this problem should be portable to
SunOS 3.X, SunOS 4.X, Ultrix 2.X, and Wollengong/VMS, or at least not
break anything in those environments.
Currently, I have a for loop which breaks large packets up, and sends them
in 2K chunks. This works. It would be nice if I could speed up the
resulting code, however. I'm hoping that fewer, larger write calls will
be faster, if I can make it work. If there are other TCP speed ups, I'd
like to hear about those, also. Thanks.
Does this problem have anything to do with the "high water mark" which
TCP(4) says has not yet been implemented?
Josh
-------- Quote: "Oh no! Its the ioctl call from Hell!"
Addresses:
joshua@atherton.com OR
sun!athertn!joshua OR
{backbone}!{decwrl!hpda}!athertn!joshua work:(408)734-9822 home:(415)968-3718joshua@athertn.Atherton.COM (Sleaze Hack) (12/14/88)
Thanks to everyone who responded to my cry for help. It seems that
SunOS 3.4 is the _SunOS from Hell_ and has many known TCP bugs.
Several people suggested replacing the TCP code with the newer "Van
Jacobson" TCP code. This in ucbarpa.berkeley.edu:pub/43net/tcp.tar.Z
(or something similar). You can annonymously ftp it.
John A. Shriver (jas@proteon.com) pointed out that there was an
option to setsockopt which did exactly what I wanted, but was only
available in 4.3bsd. With 4.2bsd I needed to patch the kernal which
adjusts the space globally. The kernal variables are tcpsendspace and
tcprcvspace.
Josh
-------- Quote: "If you haven't ported your program, it's not
Addresses: a portable program. No exceptions."
joshua@atherton.com OR
sun!athertn!joshua OR
{backbone}!{decwrl!hpda}!athertn!joshua work:(408)734-9822 home:(415)968-3718