rhxk has asked for the wisdom of the Perl Monks concerning the following question: 

this may be a dumb question, but in any case here it is.

within the same machine, I'm using unix domain socket 
server/clients for communication. How can i get the 
client script send back a result to the server script?


here's my goal. i have 2 machines on the same network. 
machine_a has multi users on it, and machine_b has only 
a single user on it. in machine_b, I have a script that 
generates some numbers. I'd like for the users on 
machine_a to call a client.script that uses the socket 
to contact my server.script on machine_a. Then my server.script
 will issue a "ssh me@machine_b /home/me/run_script".

So far I've been able to do this. however, how would I

get my server.script to send back the results to 
client.script so the users can know of the results 
produced on machine_b?

thanx for any input

Replies are listed 'Best First'.
Re: a dumb socket question
by beable (Friar) on Jul 14, 2004 at 23:38 UTC
    Hey, you didn't post any code! In general, to send a message on a socket, use the print Socket $msg function. You should read the perlipc documentation for lots of examples.
[reply]
[d/l]
Re: a dumb socket question
by rupesh (Hermit) on Jul 15, 2004 at 05:32 UTC
[reply]
Re: a dumb socket question
by castaway (Parson) on Jul 15, 2004 at 06:55 UTC
    Are you stuck on reading the results of the ssh call, or sending them to the client? You didn't say. Also, why does the server script call the run_script using ssh, if they are on the same machine? Surely you could skip that part and just call the run_script directly? (Using backticks or system, backticks will get you anything the script prints to STDOUT, eg: my $result = `run_script`;.

    To return it to the client, you just need to print that information to the socket.

    C.

[reply]
[d/l]
      I'm stuck on sending the result back to the client.
      I think if I read the perlipc's doc as suggested by beable, it'll help
      but in any case here's the code: 
      
server.script:


use Socket;
($Program = $0) =~ s@^.*/@@;

$file = "/tmp/socket.$Program";
$addr = sockaddr_un($file);
 
socket(SERVER, PF_UNIX, SOCK_STREAM, 0) || die "Could not create socke
+t: $!";
unlink("$file");
 
bind(SERVER, $addr) || die "Could not bind: $!";
 
listen(SERVER,SOMAXCONN) || die "Could not listen: $!";
 
while (accept(CLIENT,SERVER)) {
    $cmd = <CLIENT>;
    if ($cmd) {
        $time = &timeStamp;
        open(CMD, "ssh2 rob\@machine_b $cmd |");
            @results = <CMD>;
        close(CMD);
      
       print @results;
    }
}
 

client.script:


use Socket;
($Program = $0) =~ s@^.*/@@;
$file = "/tmp/server.script";
 
&Message("/home/me/run_script -r -s a1 -avg");
 
sub Message {
    my ($cmd) = @_;
    my $level = 1;
    if (socket(SOCKET, PF_UNIX, SOCK_STREAM, 0)) {
        connect(SOCKET, sockaddr_un($file)) || die "Could not connect:
+ $!";
        print SOCKET $cmd;
        close SOCKET;
    } else {
        print "I couldn't connect";
    }
}

      [download]
      OK, the client.script sends the query to server.script,
      and server.script runs the cmd & prints it. how do i get it
      to return the results to the client.script so the client.script
      can print the result? (I think i should go and read the perlipc's doc)
      thanx...
[reply]
[d/l]
        How about writing the result to the CLIENT socket? Sockets are bidirectional, and the client script is already connected to the server. I don't see any synchronization issues. 
        # server
@results = <CMD>;
print CLIENT @results;

# client
print SOCKET $cmd;
@results = <SOCKET>;

        [download]

        Why do you have a separate server and client? Since they are running on the same machine, wouldn't it be easier to just have the client script do the ssh command? The only reason I can think of is that the server script is running as a different user with ssh privledges.

[reply]
[d/l]

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