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From: frechett@spot.Colorado.EDU (-=Runaway Daemon=-)
Newsgroups: comp.unix.questions
Subject: Perl Socket problem
Summary: ^C locks up socket with perl server
Keywords: sockets perl
Message-ID: <1991May31.095020.15271@colorado.edu>
Date: 31 May 91 09:50:20 GMT
Sender: news@colorado.edu (The Daily Planet)
Organization: University of Colorado, Boulder
Lines: 75
Nntp-Posting-Host: spot.colorado.edu


I have created an interesting server that runs on my machine.  It allows 
people to browse through an archive that I haev of hp48sx programs.  
The server is written in perl and it runs on a port of my machine.
Code fragment follows.
[deleted]
$sport = $port;  # sport is used by me for record keeping;
print "Starting server on port $port\n";
unshift(@INC,"/users/en-ecen/frechett/perl");
               require 'socket.ph';

               $sockaddr = 'S n a4 x8'; # Template for pack
# get protocol from /etc/protocols
               ($name, $aliases, $proto) = getprotobyname('tcp');
# get service by protocol name 
               ($name, $aliases, $port) = getservbyname($port, 'tcp')
                    unless $port =~ /^\d+$/;

               $this = pack($sockaddr, &AF_INET, $port, "\0\0\0\0");

               select(NS); $| = 1; select(stdout);
# Open socket
               socket(S, &PF_INET, &SOCK_STREAM, $proto) || die "socket: $!";
               bind(S, $this) || die "bind: $!";  # Bind name to socket.
               listen(S, 5) || die "connect: $!"; # Listen for connection

               select(S); $| = 1; select(stdout);

CONNECTION:         for (;;) {
                 do appendit("$sport> Listening again\n"); # Log it
                    ($addr = accept(NS,S)) || die $!
                 do appendit("$sport> accept ok\n"); # Log it
# Get Specifics on connection from addr
                    ($af,$port,$inetaddr) = unpack($sockaddr,$addr);
                    @inetaddr = unpack('C4',$inetaddr);
                do  appendit("$sport> $af port=$port Inet address @inetaddr[0].@inetaddr[1].@inetaddr[2].@inetaddr[3]\n");
# Main loop
                         select(NS);
	reset $privledged;   # Make sure privledged flag is clear. 
	do motd();
LINE:                 while (<NS>) {   # Start main loop.. Reading socket
                         chop; 
[deleted]

This is what opens the socket and gets it running.. Everthing happens 
inside this while loop.  Now this is the problem.  If someone connected to the
server from outside presses control-C it locks up the connection.  If tehy just
disconnect and come back everything is fine and if they stay connected with it
in this state teh server eventually dies.  My first try was to catch it 
with 
SIG{'INT'} but someone pointed out that this only works if connected to a tty
which appears to be true.  If I kill the server from my machine with ^C it
catches it fine and does what I want.. But when a user presses control-C it 
still doesn't catch it.  IT doesn't matter where they are or what they are
doing, if they press control-C it locks.  

SO, this leads me to believe that it is a socket problem and although there are
alot of perl hackers out there, not as many have played with sockets.  What I
need to know is if there is something special about sockets and connections of
this type that would create a problem such as this?  Is there some other way
that I can open the socket to prevent this with the same results as far as
actual operation?  I really need to work this out.  

Hmmmmmmmmmmmmmmmmmmmmmmmmmm.... Just in the last 30 seconds I found out
something else related.. I tried a few different control characters on the
server to see if anything else would kill it.  ^C ^\ and ^O all locked up the
connection.  On a hunch I toggled the autoflush on sendINT of telnet and now
none of those three control characters will do it.. This is frustrating 
because now I can't track it down to anything in particular but the combination
of an interupt and flush seem to kill it.  

Any ideas as to what might be wrong?  

	ian 
-=Runaway Daemon=-           (UNIXOPS  University of Colorado at Boulder)