Re: mystery NCSA httpd problems on

Jon P. Knight (
Sat, 28 Jan 1995 21:04:18 +0100

On Sat, 28 Jan 1995, John Labovitz wrote:
> Most of the time, the server works well. But occasionally,
> connections made to the HTTP server will hang, with
> xmosaic saying 'Making HTTP connection...' and eventually
> timing out. If I cancel the connection (click the
> spinning earth) and try again, sometimes the connection
> will succeed, but more often it will hang again. If I
> retry 10-20 seconds later, the connection will usually
> succeed. Oddly, either I get a connection quickly, or
> it never comes through.

I found the same thing with an NCSA httpd 1.3 server that we were using to
distribute an e-journal on campus. The articles in the journal had lots
of maths and these were handled with inlined images. A single article
could thus have anywhere upto a couple of hundred inlined images in it.

Most of the time the server worked fine, but if it was used in a classroom
setting with 20 or 30 clients all hitting the server at once, we'd see the
same problem as you. There are several things you can try in order to fix it:

1) Run the server standalone rather than from inetd. This means that the
server won't have to reread its config file.

2) Turn off identd logging if you don't need it. This uses another TCP
connection which can be a limited resource on a busy WWW host.

3) Look in the httpd source and find any calls to listen(). These usually
specify a queue length of 5 TCP connections to listen for. I upped it to

Anyway, I did 1) and 3) and it seemed to fix our problem.


Jon Knight, Research Student in High Performance Networking and Distributed
Systems in the Department of _Computer_Studies_ at Loughborough University.
* It's not how big your share is, its how much you share that's important *