I am learning Perl at basic level, I write a program that use Socket client to do a simple task:
when it receive any message from Server, print it to screen and send an "OK" message to server.
But on screen, seem my code does not print any. Here is the code, i tested on Windows and also on Ubuntu but it seem not able to print.
I found a link Print: producing no output and
this one but it does not help.
I using
perl -v
This is perl 5, version 30, subversion 0 (v5.30.0) built for x86_64-linux-gnu-thread-multi
(with 50 registered patches, see perl -V for more detail)
Code:
use strict;
use warnings;
use IO::Socket;
my $socket = new IO::Socket::INET (
PeerAddr => '127.0.0.1',
PeerPort => '8112',
Proto => 'tcp',
);
die "cannot connect to sever $!n" unless $socket;
print "connected to server";
$socket->autoflush();
$socket->send("OK");
while (1) {
# receive a response of up to 1024 characters from server
my $response = "";
$socket->recv($response, 1024);
chomp $response;
print STDOUT $response;
$socket->send( "OK");
}
As comment from #ikegami I appended LF (\n) character to string and it print out normally. So just change to.
print "connected to server\n";
Related
I'm following this guide explaining how to do a server using IO::Async but I'm having issues with my client code. I have it where I send first then receive. This makes me press enter on each client before receiving any data. I figured I'd have to listen till I wanted to type something but I'm not really sure how. Below is my current client code.
use IO::Socket::INET;
# auto-flush on socket
$| = 1;
# create a connecting socket
my $socket = new IO::Socket::INET (
PeerHost => 'localhost',
PeerPort => '12345',
Proto => 'tcp',
);
die "cannot connect to the server $!\n" unless $socket;
print "My chat room client. Version One.\n";
while (1) {
my $data = <STDIN>;
$socket->send($data);
my $response = "";
$socket->recv($response, 1024);
print ">$response";
last if (index($data, "logout") == 0);
}
$socket->close();
I actually had this problem myself a few weeks ago when trying to make a client/server chat for fun.
Put it off until now.
The answer to your problem of having to hit enter to receive data, is that you need to use threads. But even if you use threads, if you do $socket->recv(my $data, 1024) you won't be able to write anything on the command line.
This isn't using your code, but here is my solution after banging my head against a wall for the last 24hrs. I wanted to add this as an answer, because though the question is out there on stackoverflow, none of the answers seemed to show how to use IO::Select.
Here is the server.pl script, it does not use threading:
#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket::INET;
use IO::Select;
$| = 1;
my $serv = IO::Socket::INET->new(
LocalAddr => '0.0.0.0',
LocalPort => '5000',
Reuse => 1,
Listen => 1,
);
$serv or die "$!";
print 'server up...';
my $sel = IO::Select->new($serv); #initializing IO::Select with an IO::Handle / Socket
print "\nAwaiting Connections\n";
#can_read ( [ TIMEOUT ] )
#can_write ( [ TIMEOUT ] )
#add ( HANDLES )
#http://perldoc.perl.org/IO/Select.html
while(1){
if(my #ready = $sel->can_read(0)){ #polls the IO::Select object for IO::Handles / Sockets that can be read from
while(my $sock = shift(#ready)){
if($sock == $serv){
my $client = $sock->accept();
my $paddr = $client->peeraddr();
my $pport = $client->peerport();
print "New connection from $paddr on $pport";
$sel->add($client); #Adds new IO::Handle /Socket to IO::Select, so that it can be polled
#for read/writability with can_read and can_write
}
else{
$sock->recv(my $data, 1024) or die "$!";
if($data){
for my $clients ($sel->can_write(0)){
if($clients == $serv){next}
print $clients $data;
}
}
}
}
}
}
And the client.pl, which uses threads:
#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket::INET;
use threads;
use IO::Select;
$| = 1;
my $sock = IO::Socket::INET->new("localhost:5000");
$sock or die "$!";
my $sel = IO::Select->new($sock);
print "Connected to Socket ". $sock->peeraddr().":" . $sock->peerport() . "\n";
#This creates a thread that will be used to take info from STDIN and send it out
#through the socket.
threads->create(
sub {
while(1){
my $line = <>;
chomp($line);
for my $out (my #ready = $sel->can_write(0)){
print $out $line;
}
}
}
);
while(1){
if(my #ready = $sel->can_read(0)){
for my $sock(#ready){
$sock->recv(my $data, 1024) or die $!;
print "$data\n" if $data;
}
}
}
There is one other problem that arises though, when the client receives data and prints it to the console, your cursor goes to a new line, leaving behind any characters you had typed.
Hope this helps and answers your question.
For a simple "just send from STDIN, receive to STDOUT" client, you could use any of telnet, nc or socat. These will be simple enough to use for testing.
$ telnet localhost 12345
$ nc localhost 12345
$ socat stdio tcp:localhost:12345
If you actually want to write something in Perl, because you want to use it as an initial base to start a better client from, you probably want to base that on IO::Async. You could then use the netcat-like example here. That will give you a client that looks-and-feels a lot like a simple netcat.
I am guessing you need to set the MSG_DONTWAIT flag on your recv call, and print the response only if it is non-null.
$socket->recv($response, 1024, MSG_DONTWAIT);
print ">$response" if ($response ne "");
I am a beginner to Perl socket programming. As of now, the server sends a string and the client responds with another string in my program. Later, if the server sends another string, the client is not able to receive it. To transfer data between the server and client for multiple times, should I include any functions?
SERVER:
#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket::INET;
my $socket;
my $clientsocket;
my $serverdata;
my $clientdata;
$socket = new IO::Socket::INET (
LocalHost => '127.0.0.1',
LocalPort => 2500,
Proto => 'tcp',
Listen => 1,
Reuse => 1
) or die "Oops: $! \n";
print "Waiting for the Client.\n";
$clientsocket = $socket->accept();
print "Connected from : ", $clientsocket->peerhost();
print ", Port : ", $clientsocket->peerport(), "\n";
# Write some data to the client
$serverdata = "This is the Server speaking \n";
print $clientsocket "$serverdata \n";
# read the data from the client
$clientdata = <$clientsocket>;
print "$clientdata";
$serverdata = "Server Again writing \n";
print $clientsocket "$serverdata";
$socket->close();
CLIENT:
#!/usr/bin/perl
use strict;
use warnings;
use IO::Socket::INET;
use Tk;
my $socket;
my $serverdata;
$socket = new IO::Socket::INET (
PeerHost => '127.0.0.1',
PeerPort => '2500',
Proto => 'tcp',
) or die "$!\n";
print "Connected to the Server.\n";
# read the message sent by server.
$serverdata = <$socket>;
print "Message from Server : $serverdata \n";
# Send some message to server.
my $name = "Client here!";
print $socket "$name";
# Read message sent by server.
$serverdata = <$socket>;
print "$serverdata";
$socket->close();
Printing of $serverdata second time in the Client side is not happening.
If you use to read message from another end, the sender must end the message with "\n".
Alternatively, you can use recv(...) so the message won't be buffered till newline character.
Just make sure your client sends a whole line. SInce you are reading with
<$clientsocket>
your server waits for a "\n" from the client.
Your server starts listening on some port. It waits until a client connects, the accepts that connection. It reads and writes a bit of data over the client connection. And then? Then it just closes the socket and exits the program.
That is not what you intended: You want the server to start waiting for the next connection. That means some kind of loop: Each time a client connects, we'll do our communication:
while (my $client = $socket->accept) {
# do something with the $client
}
I recommend you read through the relevant sections of perldoc perlipc, but keep in mind it uses outdated best practices, so don't directly copy anything.
I'm trying to create a chat server using sockets in Perl. However, when I run the Server program I get the error:
"ERROR:(9)(Bad file descriptor)(6)(+The handle is invalid) at Server.pl line 21."
and when I run the client program I get the error:
"Cannot create the socket: No connection could be made because the target machine
actively refused it."
Here is the Server program:
#!usr/bin/perl
#server.pl
use IO::Socket;
$| = 1;
print "Server Program\n";
my $lp = 12000;
my $server_socket, $new_client, $addr, $port;
$server_socket = new IO::Socket::INET (
LocalHost => '127.0.0.1',
LocalPort => $lp,
Proto => 'tcp',
Reuse => 1) or die "Cannot create the socket: $!\n";
print "Server started at port $lp \n";
while (1) {
$new_client = $server_socket->accept() or die sprintf "ERROR:(%d)(%s)(%d)(+%s)", $!,$!,$^E,$^E;
$addr = $new_client->peerhost();
$port = $new_client->peerport();
print "Connected to client at $addr at port $port ";
while(<$new_client>) {
print "Following is the text entered by client: \n";
print "$_";
}
print "Client now disconnecting..\n";
close $new_client;
}
$server_socker->close();
And here is the client:
#!usr/bin/perl
#client.pl
use IO::Socket;
$| = 1;
print "Client Program\n";
my $lp = 12000;
my $client_socket = new IO::Socket::INET (
PeerHost => '127.0.0.1',
PeerPort => $lp,
Proto => 'tcp',
Reuse => 1) or die "Cannot create the socket: $!\n";
print "Server connected at port $lp \n";
print "Enter the text to sent to the server: \n";
$user_input = <>;
chomp $user_input;
print $plient_socket;
$client_socket->send($user_input);
$client_socket->close();
I am new to this and I'm not getting where I'm going wrong. Could anybody help?
You trying to accept a connection from a socket that's not listening. Add
Listen => SOMAXCONN,
And now for off-topic comments about your code:
Always use use strict; use warnings;. It will highlight some other problems with your code.
It doesn't make any sense to relative paths on the shebang line. You're missing a /.
On the style front, it's considered bad form to declare variables ahead of where they are used. The whole point of declaring variables is to limit their scope, so declaring them at the top of the program defies the purpose.
LocalHost => '127.0.0.1' (better written as LocalHost => INADDR_LOOPBACK) makes it so you can only receive connections from 127.0.0.1. That can be useful, but I don't know if you did that intentionally. The default, INADDR_ANY, allows connections from any interface.
My client.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $name = '172.20.10.189'; #Server IP
my $port = '7890';
my $socket = IO::Socket::INET->new('PeerAddr' => $name,
'PeerPort' => $port,
'Proto' => 'tcp') or die "Can't create socket ($!)\n";
print "Client sending\n";
while (1) {
my $msg = <STDIN>;
print $socket $msg;
print scalar <$socket>;
}
close $socket
or die "Can't close socket ($!)\n";
My server.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $port = "7890";
my $socket = IO::Socket::INET->new('LocalPort' => $port,
'Proto' => 'tcp',
'Listen' => SOMAXCONN)
or die "Can't create socket ($!)\n";
while (my $client = $socket->accept) {
my $name = gethostbyaddr($client->peeraddr, AF_INET);
my $port = $client->peerport;
while (<$client>) {
print "[$name $port] $_";
my #out = `$_`;
print #out;
print $client "$.: #out";
}
close $client
or die "Can't close ($!)\n";
}
die "Can't accept socket ($!)\n";
My client is sending a command (ls -lrt /) to the server and Server is supposed to run that command and send output to the client back.
Problem:-
The command is executed successfully on the server but it sends only first line to the client. If I press any key from client again the next line of output is sent to the client.
Or tell me how to send multiple line output to back to client.
Any help would be appreciated.
Thanks
Abhishek
The Server sends all lines to the client, the client however chooses to read only one line:
print scalar <$socket>;
If you remove the scalar, it should work. However, your architecture is still a security nightmare.
All servers should run in taint mode (-T switch).
Never blindly execute commands that a clients sends you. Only execute commands that pass a very strict validation test, do not run commands that just don't look malicious.
Perhaps you are trying to duplicate SSH, you might want to look at that program instead.
Your server doesn't do any kind of authentication. At least it logs all inputs.
It was a silly mistake... and I have fixed the first issue as follows and got multi-line output on the client side...
Client.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $name = '172.20.10.189'; #Server IP
my $port = '7890';
my $socket = IO::Socket::INET->new('PeerAddr' => $name,
'PeerPort' => $port,
'Proto' => 'tcp')
or die "Can't create socket ($!)\n";
print "Client sending\n";
while (1) {
my $msg = <STDIN>;
print $socket $msg;
while (<$socket>)
{
print "\n$_";
}
}
close $socket
or die "Can't close socket ($!)\n";
BUT there is one more issue -
I want my client to keep sending few other commands one after another until I close the client manually and receive output.
The problem is - It receives output of the first command only..
Can anyone now help me on this?
I've bumped into a strange problem. I wrote a little daemon in Perl which binds a port on a server.
On the same server there's a LAMP running and the client for my Perl daemon is a php file that opens a socket with the daemon, pushes some info and then closes the connection. In the Perl daemon I log each connection in a log file for later usage.
My biggest problem is the following: between the moment when the php script finishes its execution there are 15-20seconds until the daemon logs the connection.
PHP Client:
$sh = fsockopen("127.0.0.1", 7890, $errno, $errstr, 30);
if (!$sh)
{
echo "$errstr ($errno)<br />\n";
}
else
{
$out = base64_encode('contents');
fwrite($sh, $out);
fclose($sh);
}
Perl daemon (just the socket part)
#!/usr/bin/perl
use strict;
use warnings;
use Proc::Daemon;
use Proc::PID::File;
use IO::Socket;
use MIME::Base64;
use Net::Address::IP::Local;
MAIN:
{
#setup some vars to be used down...
if (Proc::PID::File->running())
{
exit(0);
}
my $sock = new IO::Socket::INET(
LocalHost => $ip,
LocalPort => $port,
Proto => 'tcp',
Listen => SOMAXCONN,
Reuse => 1);
$sock or die "no socket :$!";
my($new_sock, $c_addr, $buf);
for (;;)
{
# setup log file
open(LH, ">>".$logs);
print "SERVER started on $ip:$port \n";
print LH "SERVER started on $ip:$port \n";
while (($new_sock, $c_addr) = $sock->accept())
{
my ($client_port, $c_ip) =sockaddr_in($c_addr);
my $client_ipnum = inet_ntoa($c_ip);
my $client_host =gethostbyaddr($c_ip, AF_INET);
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime time;
$year += 1900;
$mon += 1;
print "$year-$mon-$mday $hour:$min:$sec [".time()."] - got a connection from: [$client_ipnum]";
open(AL, ">>".$accessLog);
print AL "$year-$mon-$mday $hour:$min:$sec [".time()."] - got a connection from: [$client_ipnum]\n";
close AL;
while (defined ($buf = <$new_sock>))
{
print "contents:", decode_base64($buf), " \n";
open(FH, ">".$basepath."file_" . time() .".txt") or warn "Can't open ".$basepath."file_".time().".txt for writing: $!";
print FH decode_base64($buf);
close FH;
}
}
close LH;
}
}
What is the thing that I do so wrong and then leads to 20seconds gap between php closing the socket after writing it and the Perl script logging the connection. Any idea?
Be gentle, I'm new to Perl :)
$new_sock is not closed explicitly, and so is not closed until the accept call. This might cause some things to hang until timeouts are hit. (I am not sure if the close will happen on entry to accept or exit from. )
Also, you are using the "<>" operator to read data from a socket. What happens if there are no newlines in the input ?
The best way to see what is actually happening is to run the process under "strace -e trace=network" and try to match up the network system call with the perl and php statements.
I am not seeing any call to flush the buffer, could you check if the delay disappears when flushing after logging?