Simple Socket Guidance



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Simple Socket Guidance

Postby polar » Tue, 28 Nov 2006 23:51:54 GMT


I'm currently working on a project in which I need to run a process on
one machine that can invoke a process on another machine over the
internet. For example, pressing [enter] on my machine will run a script
on another machine (with static IP) arbitrarily far away.

I'm new to this sort of coding, so I just wanted to get a rough idea
what I should be diving into. This would be the job for a socket,
correct? Or servlet? Am I right in looking at Ruby and Python? If you
could just steer me in the right direction, I can manage. Thanks a lot.

Re: Simple Socket Guidance

Postby ipnwsec » Thu, 30 Nov 2006 08:02:11 GMT


what u need to do is write a client server program.
Server runs on a remote machine on which u need to invoke a process.
and client runs on your machine.

You can implement these client servrers using sockets based on tcp.

When ever you press ENTER on client machine send a message on the tcp
connection from client to server. On server decode the message and
invoke a process using fork..etc.

If you want any more info please feel free to contact

you can post your further questions regarding this on this group :


Similar Threads:

1.Newbie: Could use tutorial guidance of experienced TCP/IP sockets programmer

2.Newbie: Could use tutorial guidance of experienced TCP/IP sockets programmer

3.Need help with a simple UNIX sockets server based on IO::Socket::UNIX

Hi. I've tried to create a simple client + server that communicate
through a unix socket.

As with all socket servers, it has a loop where it waits for

while ($client = $sock->accept()) {
  # handle client here

The problem is that $sock->accept() is returning undef on each
alternate client connection with error "No child processes".

I made this temporary workaround that does work but of course I must be
screwing up somewhere else:

while ($client = $sock->accept() || $client = $sock->accept()) {
  # handle client here

I hope someone can help or provide an example. I've included the client
+ server code below for those who are interrested in taking a peek.

Craig Manley

############ client ############
#!/usr/bin/perl -w
use strict;
use IO::Socket;

my $sockname = 'mysocket';

my $client = IO::Socket::UNIX->new('Peer' => $sockname,
                                   'Type' => SOCK_STREAM,
                                   'Timeout' => 50) or die "$0: error
connecting to '$sockname': $ [at] \n";
my $pid = fork();
unless(defined($pid)) {
  die("Fork this! I cannot forking fork!\n");
if ($pid) {
  waitpid($pid, 0);
else {

sub write_sock {
  for (1..10) {
    print $client "testline number $_\n"; # print to socket
  print $client "\n"; # empty line causes server to terminate
  print "Done writing.\n"; # (goes to stdout, not socket)

sub read_sock {
  while (my $line = <$client>) {
    print $line; # report to stdout
    # simulate someone reading slooowly (50ms/line):
    select(undef, undef, undef, 0.05);

########### server ############
#!/usr/bin/perl -w
use strict;
use IO::Socket;
use POSIX ":sys_wait_h"; # (for WNOHANG)
use Data::Dumper qw(Dumper);

# example using unix domain socks
# once the file is created as a socket, any client can
# interact with it

my $sockname = 'mysocket';

service_clients( get_sock() ); # wait for incoming requests

sub get_sock {
  unlink $sockname;
  my $sock = IO::Socket::UNIX->new('Local'  => $sockname,
                                   'Type'   => SOCK_STREAM,
                                   'Listen' => SOMAXCONN) || die "$0:
error starting daemon on '$sockname': $ [at] \n";
  # you might want to change permissions and ownership, e.g.:
  #chmod 0600, $sockname;
  #chown scalar getpwnam('nobody'), 0, $sockname;
  return $sock;

sub service_clients {
  my $sock = shift;
  $SIG{CHLD} = \&reaper;
  my $client;
  while ($client = $sock->accept()) { # Why the hell does it return
undef on the next iteration?
  # while ($client = $sock->accept() || $client = $sock->accept()) { #
This strangely enough does work.

    # fork yet another process to prevent buffer deadlock. one proc
writes to
    # the sock, the other reads the deamons response
    my $pid = fork();
    unless(defined($pid)) {
      die("Fork this! I cannot forking fork!\n");
    if ($pid) { # parent
      print "$pid $$: I'm the parent and am going to wait for another
      close($client); # no use to parent
      next; # be ready for another client
    print "$pid $$: I'm the child and I'm going to service the
    # child
    close($sock); # no use to child
    print "$pid $$: I'm the child and I'm going to exit.\n";
    exit; # terminate child
  print "Damnit! I'm the server and I finished unexpectedly: $!\n";

sub process_requests {
  my $client = shift;
  $0 = "unixsockd: handling requests...";
  # read from client until empty line which causes it to close
  while ( my $line = <$client> ) { # read line from socket
    if ($line =~ /^\s$/) {
      last; # exit on empty line
    # put some more useful code here to read each line or whatever...
    printf $client "%s: %s, handled by PID %d\n",
    scalar localtime(time), $line, $$;
    # return something to client

sub reaper {
  while (waitpid(-1,WNOHANG) > 0) {}
  $SIG{CHLD} = \&reaper;

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7. Simple Socket program hangs system on recv()

8. Help needed in a simple UDP socket program

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