Perl, Sockets and TCP/IP Networking.

An simplified introduction to sockets

Sockets are a mechanism that allows programs to communicate, either on the same machine or across a network. The way it works is pretty simple: Each machine on a network is identified by some address. In this tutorial we will talk about tcp/ip networking, so by network address we mean an IP address. (like 192.168.4.4) Apart from the IP address that specifies a machine, each machine has a number of ports that allow handling multiple connections simultaneously.

A program that wishes to receive a connection from another program, asks the operating system to create a socket and bind it to some port. Then the program sits and listens on the socket it has created to receive incoming connections. The other program also creates a socket for communicating witht he receiver. The caller needs to specify the IP address and the port number of the receiving end. If all goes well, and as we will see shortly, the two programs establish a communication through the network using their sockets. The two programs may exchange information, each by writing to and reading from the socket it has created.

Can I do this with Perl?

Sure. Perl provides support for the socket API natively. Although the interface is not that bad anyway, there is also a very convenient module, IO::Socket that works like a wrapper on the native API and provides a simpler and easier way to deal with sockets. We'll use IO::Socket in this tutorial to demonstrate writing two simple programs that communicate with sockets.

The Receiver

The first thing we need to do is to create a socket. We will use it to receive connections. The code below shows how to create a receiving socket. Note that we need to specify the local hostname and the port to which the socket will be bound. Of course, if the port is already in use this call will fail. Also note the 'Listen' parameter: this is the maximum number of connections that can be queued by the socket waiting for you to accept and process them. For the time being we will only accept a maximum of one connection at any time. (This means that a connection attempt while we're dealing with another connection, will return with an error like 'connection refused') Finally the 'Reuse' option tells the system to allow reuse of the port after the program exits. This is to ensure that if our program exits abnormally and does not properly close the socket, running it again will allow opening a new socket on the same port.

1 use IO::Socket;
2 my $sock = new IO::Socket::INET (
3                                  LocalHost => 'thekla',
4                                  LocalPort => '7070',
5                                  Proto => 'tcp',
6                                  Listen => 1,
7                                  Reuse => 1,
8                                 );
9 die "Could not create socket: $!\n" unless $sock;

Now the socket is ready to receive incoming connections. To wait for a connection, we use the accept() method which will return a new socket through which we can communicate with the calling program. Information exchange is achieved by reading/writing on the new socket. The socket can be treated like a regular filehandle.

10 my $new_sock = $sock->accept();
      11 while(<$new_sock>) {
      12    print $_;
      13 }
      14 close($sock);

The Caller

The other side of the communication is even simpler. All we need to do is to create a socket specifying the remote address and port. The constructor will return a socket object after the connection has been etablished, and we may start sending data right away by writing onto the socket like any other filehandle.

1 use IO::Socket;
2 my $sock = new IO::Socket::INET (
3                                  PeerAddr => 'asomatos',
4                                  PeerPort => '7070',
5                                  Proto => 'tcp',
6                                 );
7 die "Could not create socket: $!\n" unless $sock;
8 print $sock "Hello there!\n";
9 close($sock);

Go ahead and try it!

You can easily try out the example programs above. All you need to do is execute the receiver first and then the sender. On the receiver end, you will see the line "Hello there!" printed on the terminal screen. If you do not have a network, you can still use 'localhost' for the hostname of both the receiver and caller just to test it out.

Synchronization

An important issue to consider in this style of communication is that the two ends must follow a commonly-agreed procedure of data exchange. Otherwise it is very easy to end up in a deadlock situation where either both ends try to read, or both ends try to write. Ther is no way to guess whether the other end has finshed sending data, unless there is some protocol of communication between them that denotes logical sections of the communication in the contents of the transmitted messages. In the example above, the model is very simplistic: The caller sends a message and closes its end of the connection, while the receiver just reads the data until it's all finished.

Usually client-server transactions consist of a caller (the client) sending a request, followed by the receiver (server) sending back a reply. In order for the server to understand when the request is finished, there is some agreed marker (such as two consecutive empty lines, or a line saying "END REQUEST") that denotes the last line in the request. The server, starts sending its reply only after this line has been received, and afterwards closes the socket. The receiver, after sending the entire request switches to reading until the socket is closed, so it will receive the reply. More complex schemes can be established in a similar mannere, according to your needs and taste. What is important is to make sure that the two ends of the communication have a way of knowing when to speak and when to listen, thus avoiding the possibility of getting locked up.

Online Documentation/Tutorials

Network Programming in Perl - a well-written introduction to network programming with practical examples.
The documentation of the Socket and IO::Socket modules that comes with your perl distribution should be a valuable reference.
There's also an article on filhandle multiplexing with select() in which we describe a method commonly use to manage multiple sockets on the same thread.

Comments


32to28	Posted at 5:27pm on Monday, March 5th, 2007
Great article, helps a ton. Great for beginners, can modify it to your own chat application. Thanks.
Akshat Mithal	Posted at 11:16am on Sunday, April 8th, 2007
Thanks it was a great note.. I created my own successful script for the first time. Thanks
Soy4soy	Posted at 12:14pm on Friday, April 20th, 2007
This helped me pick perl up where I left off years ago... thanks!
rajiv	Posted at 11:21pm on Thursday, May 17th, 2007
Thanks it was a great note..
Emin Gabrielyan	Posted at 6:14am on Monday, May 21st, 2007
The listener script of the example does not work with UDP
Emin Gabrielyan	Posted at 12:35pm on Monday, May 21st, 2007
Here is a script for receiving and printing UDP packets: === use IO::Socket; $server = IO::Socket::INET->new(LocalPort => '5060', Proto => "udp") or die "Couldn't be a udp server on port $server_port : $@n"; my $datagram; my $MAX_TO_READ = 2048; while ($user=$server->recv($datagram,$MAX_TO_READ)) { print "---n"; print $datagram; } close($server); === Here is the screenshot of the script, which receives REGISTER messages from a SIP phone: === $ perl a5.txt --- REGISTER sip:192.168.1.8 SIP/2.0 Via: SIP/2.0/UDP 192.168.1.10;branch=z9hG4bK994c1f6fcb609bef From: ;tag=dace27af55f4699b To: Contact: Supported: replaces Call-ID: 599f793881392bc1@192.168.1.10 CSeq: 100 REGISTER Expires: 150 User-Agent: Grandstream BT110 1.0.8.33 Max-Forwards: 70 Allow: INVITE,ACK,CANCEL,BYE,NOTIFY,REFER,OPTIONS,INFO,SUBSCRIBE Content-Length: 0
aussie	Posted at 4:52pm on Wednesday, May 30th, 2007
Well written, easy to follow and very informative. Keep up your good work!
tejaswi	Posted at 3:11am on Wednesday, June 13th, 2007
Can i get a simple perl server script DGRAM
Sam,.	Posted at 5:50am on Thursday, June 21st, 2007
Great article. it helped me a lot to understand the socketing very easily.. thanx a lot..
Sam	Posted at 2:47am on Friday, June 22nd, 2007
This helped me a lot. could you please post an article like this with forking, threading using socket programming?
Guilherme Arthur	Posted at 5:17pm on Friday, June 22nd, 2007
Dude! You saved my life! XD Thankx very much! =D
vijay	Posted at 12:00am on Sunday, July 1st, 2007
Great article. it helped me a lot to understand the socketing very easily, this is giving the information , how it works well. first of all, if i want to know what is TCP/IP and Perl ( I Understand the functionality of TCP/IP), can any one expalin me from scratch. it will be useful in my QA Career
Anonymous	Posted at 12:18am on Friday, July 6th, 2007
nice way to do cl-server perl script
anonymous	Posted at 6:28am on Monday, July 23rd, 2007
nice, this article helped me a lot, keep it up, next one do UDP and maybe find a way to use udp with the quake2 protocol
Smaregow	Posted at 9:47am on Tuesday, July 24th, 2007
Hi, Can any one help me in solving my questions...my project is some thing like explained below: My project configuration is something like this... Clients .Net Message Server Various Servers TCP/IP is between Clients and .Net message server...and .Net message server is with other servers through COM. I have 10 clients application and each client has arround few messages...those messages(request) will be send to .Net Message Server which will routes these requests various other Servers and gets the appropriate responses. By keeping all input messages in the FLAT File I want to Automate the sending and receiving messages using the PERL script and also I want to compare the receving messages aginst the Existing good known results. My basic questions are.... Is it possible to automate this using PERL script? OR Do you recomend any other scripting tool to automate this project? Could any body please help me in taking the right decision? Many Thanks in Advance, Smaregow
colin	Posted at 10:15am on Wednesday, August 1st, 2007
pls give me my tcp/ip to play warlords battlecry
Cat	Posted at 7:21am on Thursday, August 2nd, 2007
I can has cheezeburger?
Wicked_Sunny	Posted at 11:29pm on Thursday, August 2nd, 2007
It was really good.. I was really looking for such article to begin with socket programming. May be I am on my way to develop My Chat application... Be ready to test my version...
Mihir	Posted at 1:18am on Saturday, August 11th, 2007
Thanks for this Simple introduction to Perl Sockets to give me a start..
kalyan	Posted at 2:27am on Saturday, August 18th, 2007
it gud but describe with starting commands to be used like intilization of socket,termination of socket e.t.c.
andy	Posted at 2:12pm on Tuesday, August 21st, 2007
any tips on "after sending the entire request switches to reading until the socket is closed." I'd love to see this example extended to illustrate this!
matt	Posted at 4:03pm on Thursday, August 23rd, 2007
I've been stuck on a problem with this regarding the read of the client filehandle...I want a server that periodically goes to check on all it's sockets with clients to see if any of them have messages...if so it'll service the sockets (all the lines of their communication) and then go back to it's normal business. The trick is I dont want to keep opening and closing new sockets and instead just keep them open and read from them when ->select tells me there's stuff there. What seems to happen however is that my client sends a number of lines of info and the server prints through the first line and then the IO::Select->select then says none of the handles are readable...the can_read returns nothing and so does select. I then wait a bit (like 9 seconds or 3 loops of my "check on the sockets") and send another message from the client...suddenly all the stored up info floods out except again the last line...I then send 5 more lines and it again only writes out the 1st an then says no more...cycle repeating.. Anyway, here's my server code and the client code is beneath it...thanks for any observations! matt #!/usr/local/bin/perl use IO::Socket; use IO::Select; my $server_socket = new IO::Socket::INET ( LocalHost => localhost, LocalPort => 7070, Proto => 'tcp', Listen => 32768, Reuse => 1, timeout => 5, ); die "Could not create socket: $!n" unless $server_socket; print "created socket $server_socketn"; $Read_Handles_Object = new IO::Select(); # create handle set for reading $Read_Handles_Object->add($server_socket); # add the main socket to the set while (1) { # forever while (1) { # keep in this loop as long as there is a readable filehandle.. # get the set of readable handles # my ($readable_handles) = IO::Select->select($Read_Handles_Object, undef, undef, 0); if (! scalar @$readable_handles) {print "nothing left to read...n";last} foreach $rh (@$readable_handles) { #print "read handle found : '$rh'n"; # if it is the main socket then we have an incoming connection and # we should accept() it and then add the new socket to the $Read_Handles_Object if ($rh == $server_socket) { # you get this when a new socket connection is formed..a new client starts and it assigns # a socket filehandle to it. #print " accept(); $Read_Handles_Object->add($client); $ClientNumber{$client}=++$CLIENT_COUNT; #print " %%% Adding '$client' to read setn"; } # otherwise it is an ordinary socket and we should read and process the request else { #print " --this is an ordinary socket '$rh'n"; $buf = $rh->getline(); # grab a line .. it shouldnt block due to the select if (! defined $buf) { # the other end of the socket closed...close our end and remove # it from the list of sockets to listen to.. print " \|FROM CLIENT ".$ClientNumber{$rh}."\| --socket closed--n"; $Read_Handles_Object->remove($rh); close($rh); last; } print " \|FROM CLIENT ".$ClientNumber{$rh}."\|$buf"; } } } # after going through the sockets I'll get back to some other work # .. I'll simulate that with a sleep 3 .. print "sleeping...n"; sleep 3; } HERES THE CLIENT : #!/usr/local/bin/perl use IO::Socket; my $sock = new IO::Socket::INET ( PeerAddr => 'palm', PeerPort => '7070', Proto => 'tcp', ); die "Could not create socket: $!n" unless $sock; while(1) { print "Message : "; chomp($message=); print $sock "$messagen"; }
matt	Posted at 4:04pm on Thursday, August 23rd, 2007
correction...palm on the client is the localhost...adjust that please ... issue still remains...
matt	Posted at 12:12pm on Friday, August 24th, 2007
it seems that my paste into the entry box stripped out some stuff...like backslash n for a return drops the backslash..watch out for that..also in the client I get stdin with that chomp($message thing but it dropped the "open angle" STDIN "close angle" ... note that to test this you can up the sleep to like 10 seconds and then while it's sleeping have the client send like 5 strings ... then when the server wakes up it prints out the first and then says no more read handles...then hit return again on the client and out it comes...if you dont like having a sleep this issue would also happen if the server took a few seconds to perform some action for one of the children while another was pumping messages into its socket.. thanks, Matt
baba	Posted at 5:17am on Tuesday, August 28th, 2007
sorry i couldnt help you at present
shekar	Posted at 3:42am on Monday, November 12th, 2007
anyone knows how to write smtp mail implementation in PERL , or graphical soket programing to implement SMTP please reply now
Shannon	Posted at 8:05am on Friday, November 16th, 2007
Anyone can help on the following problem: (Perl IO::Socket module)The client will prompt the user for two numbers and send them to the server. After server add the numbers and send back to client, THEN client will display the result to the user.
Richard	Posted at 3:39am on Tuesday, November 20th, 2007
Hi, The example on top is a one way communication. I would like to send back a message from the serber, to the client: 1) Client sends "Hello there!" 2) Server prints on the screen "Hello there!", and then replies the number of bytes received. 3) Client prints out 12 (the number of bytes sent), and then terminates. Is there a quick way to do this, or do I have to set up another port for the answer? Regards, /Richard
krishna	Posted at 3:57am on Tuesday, November 27th, 2007
use strict; use Socket; # use port 7890 as default my $port = shift \|\| 7890; my $proto = getprotobyname('tcp'); # create a socket, make it reusable socket(SERVER, PF_INET, SOCK_STREAM, $proto) or die "socket: $!"; setsockopt(SERVER, SOL_SOCKET, SO_REUSEADDR, 1) or die "setsock: $!"; # grab a port on this machine my $paddr = sockaddr_in($port, INADDR_ANY); # bind to a port, then listen bind(SERVER, $paddr) or die "bind: $!"; listen(SERVER, SOMAXCONN) or die "listen: $!"; print "SERVER started on port $port n"; # accepting a connection my $client_addr; while ($client_addr = accept(CLIENT, SERVER)) { # find out who connected my ($client_port, $client_ip) = sockaddr_in($client_addr); my $client_ipnum = inet_ntoa($client_ip); my $client_host = gethostbyaddr($client_ip, AF_INET); # print who has connected # send them a message, close connection print CLIENT "Smile from the servern"; print "got a connection from: $client_host"," [$client_ipnum] n"; close CLIENT;}
Pasini	Posted at 3:29am on Thursday, November 29th, 2007
Hi, I am new to internet programming but I have some years with electronics, microcontrollers and windows apps. My question is simple and I think PERL may be the right way to solve it. Please help me: 1) I want a socket server and a web/e-mail/ftp server in the same machine, to which I don´t have direct access since it is my ISP machine in another city. 2) How do I create the socket server ? Is it a PERL module and this lines of code from other messages ? How do I install it and how do I run it (I cannot run it from command line !!!) ? Nobody will be able to type commands from command line to run it ! 3) The client will be something like hyperterminal from windows (actually an equipment). Can you suggest a book or tutorial that teaches me how to work with server sockets, install and run it ? Thanks in advance, Pasini
Sandy	Posted at 11:29pm on Tuesday, December 4th, 2007
Very simple and easy to understand..Thanks buddy!
Allen Alex	Posted at 2:37am on Thursday, December 13th, 2007
GREAT ARTICLE thanks buddy...
Dale	Posted at 11:08am on Thursday, December 13th, 2007
This script was a great help! Thanks!
gammy	Posted at 5:13am on Tuesday, December 18th, 2007
I must say I cannot get this example working at all - I've been tinkering with it for about an hour now and it just doesn't work as explained at all. http://pastebin.ca/821913 shows my code(pretty identical to above)
gammy	Posted at 8:32am on Tuesday, December 18th, 2007
Ah, I am but a fool! Solved it. Excellent!
james	Posted at 12:38am on Sunday, December 30th, 2007
Nice article, easy to understand. Thanks!!
Ranjit	Posted at 11:20am on Friday, January 18th, 2008
How do I incorporate variables into the script above. I got it working, but I am having trouble transferring variables.
Jack	Posted at 11:56am on Tuesday, January 22nd, 2008
Many thanks. Just a question. How can the server sends a reply to the client?
steve	Posted at 8:36pm on Tuesday, January 22nd, 2008
excellent... this little bit of code helped me create a simple remote admin script for video switching units with absolutely no previous experience with perl. thanks!
Paras	Posted at 10:56am on Thursday, January 24th, 2008
Thanks a ton man.. it really helped me in implementing customized script for sending real time logs to central log server (syslog_ng). Again, thanks a ton for it....
manohar	Posted at 11:47am on Thursday, February 21st, 2008
can any one suggest with the perl scripts used in automation of SIP testing
Marko	Posted at 7:29am on Saturday, February 23rd, 2008
Hello, I am also looking for a perl script to handle SIP testing. - The idea is to have a simple scrit (ex ua.pl) that sends "template files" as argument (ex: ua.pl template.txt). - The ua.pl shall sends the data over udp to peer server ip address on port 5060 for instance. - Template files are not part of the script but written by user .. copy/past from some call flows. So will be happy if some one post a simple script that reads the file (template) and sends it to server.
ronie	Posted at 4:58pm on Monday, February 25th, 2008
Hello, I am new to perl and have been doing some reading. Can someone tell me how to call a script in another host? This article has really helped me, i have been able to create my client and server, but i need to know how to call a sript to do things for me while connecting to the server. Thanks
Erwin	Posted at 6:55am on Wednesday, February 27th, 2008
I just implemented the two scripts (server and client) and work fine the first time. While server is runnin in the background I run the client the first time and works, but the second time I run the client I get an error "could not create socket: Connection refuse" then I see the server teminating. Something missing on the code?
harry	Posted at 2:02pm on Thursday, February 28th, 2008
Erwin, you need to put the $socket->accept() in a loop
Benjamin	Posted at 1:22am on Tuesday, March 4th, 2008
Hello, I'm just trying to find a possiblity to check if a specific port (e.g. 80) is listening unter Solaris. But tbh i'm very new to all of that and i thought that active probing (trying to establish a connection to the port, see if it works and cancel the connection if necessary) with a result of 0 or 1 would be best. I found that article with google but tbh it doesn't help me that much :( Cheers, Benjamin
Anonymous	Posted at 1:10pm on Thursday, March 6th, 2008
Harry, Thanks, it works as designed. Now I'm looking for a similar client but for Windows, it would be great if done in VBS. Thanks again.
niks	Posted at 2:37am on Tuesday, March 25th, 2008
For all those who want to write back something to client, you can use the print statement. e.g. 1 use IO::Socket; 2 my $sock = new IO::Socket::INET ( 3 LocalHost => 'thekla', 4 LocalPort => '7070', 5 Proto => 'tcp', 6 Listen => 1, 7 Reuse => 1, 8 ); 9 die "Could not create socket: $!n" unless $sock; 10 my $new_sock = $sock->accept(); At this step you can employ specific code to read something from client and then when its time to write something to client this is what you do: print $new_sock "Here comes the response from server...n"; Thats it!. Depending upon the requirement above code may get more complex, but this atleast gives you some idea. --Niks.
dwight	Posted at 2:05pm on Monday, March 31st, 2008
Could Anyone Help Me With This Socket Connection? I'm attempting to tcp a microcontroller. I'm able to do it with vb from a laptop, but I want to communicate from a web page using Perl. I need to send the characters "F5F0" to the micro controller at ipaddress 24.180.20.119 port 59004. The ipaddress (not real) is to my router and the port is the port of the micro controller. I'm trying this code, it does not reurn an error when udp is used, but returns an internal sever error when I change to tcp: #!/usr/local/bin/perl -w use strict; use IO::Socket::INET; my $sock = new IO::Socket::INET ( PeerAddr => '24.180.20.119', PeerPort => '59004', #Proto => 'tcp', Proto => 'udp', ); die "Could not create socket: $!n" unless $sock; print $sock "F5F0"; close($sock); print "Content-type: text/htmlnn"; print "Hi there!n"; exit; The vb program that does work uses winsock like this: If Winsock1.CtlState MSWinsockLib.StateConstants.sckClosed Then Winsock1.Close() Winsock1.RemoteHost = IP_Address.Text Winsock1.RemotePort = 59004 Winsock1.LocalPort = 0 Winsock1.Connect() If Winsock1.CtlState = MSWinsockLib.StateConstants.sckConnected Then If RadioButton6.Checked = True Then Call Winsock1.SendData("F5F0") endif
Lar	Posted at 10:07pm on Wednesday, April 16th, 2008
hey everybody, everything looks good and easy, but being a bit defensive minded, can someone point me to resources about checking to make sure we don't get DOS'ed or similar? Thanks!
Jay	Posted at 12:04pm on Tuesday, April 22nd, 2008
Thanks a lot, its simple and easy in your demonstration. Great effort mate.
Nhung	Posted at 6:52am on Wednesday, April 30th, 2008
In the beginning, I used your first program, but it did not work. I dont know why? I installed Apache and Perl on Windows xp? Is that a problem? Do I need to setup something with Perl and Apache to use socket?
bipul	Posted at 10:23pm on Wednesday, April 30th, 2008
Great Article, well written. Atleast some basic concepts got cleared.
kuji	Posted at 11:18am on Tuesday, June 17th, 2008
I was wondering if there was a way to actually control the pins of the LPT port with a perl script(I more interested in the jetdirect 310).Can I have a basic sample script
Firehawk	Posted at 12:22pm on Wednesday, July 2nd, 2008
I was able to setup the socket test however, I want it to print to a log file with a date and time stamp. Is there some place I can read on how to or does some have an example? I basically want to update a log file with the entry and then roll the log daily. #! /usr/bin/perl -w use IO::Socket; my $msg = ""; my $socket = IO::Socket::INET->new ( PeerAddr => 'localhost', PeerPort => '4035', Proto => 'tcp', Type => SOCK_STREAM, Blocking=> 0) or die "Could not create socket: $!n"; print $socket "0006HI"; my $sock_addr = recv($socket,$msg,190,0); if ($msg =~ /0190HI/) { print "ISD Switch is upn"; print "response is $msgn"; } close($socket);
KhinMyatMyatSoe	Posted at 10:49pm on Wednesday, July 2nd, 2008
Reexplain this Website in words, no programming language. This Website is very useful.
Thom	Posted at 11:05pm on Wednesday, July 9th, 2008
Any idea on how you could call a servlet this way, writing a GET command?
Ashton	Posted at 10:02am on Monday, August 18th, 2008
So my problem is this: I need a check to transfer FROM a linux box TO a windows box. It needs to send the command name and the flags to be used. I have successfully used this socket protocol to do so, but it dies every time it's done, which is a problem. I need it to be perpetual, like a web server. How do I do that?
Prashant	Posted at 4:03am on Tuesday, August 19th, 2008
i want to read the data frn http port i jst simply want create log watever site hasbeen accesed. plzz help me out ASAP..
Bthoj	Posted at 11:20am on Wednesday, August 20th, 2008
With the above codes... how do you make the client and server automatically scan for an open port to use? I also want to be able to have the client print out the port being used to the server and the server displays the port number?
Roland	Posted at 1:39am on Friday, September 12th, 2008
Many thanks for this tutorial.
ram	Posted at 11:17pm on Monday, September 15th, 2008
Thank you so much for the beautiful explanation of sockets thank you so much
ANISH.H.DAS	Posted at 5:47pm on Tuesday, September 23rd, 2008
Thank you so much for the beautiful explanation of sockets
Anjali	Posted at 11:04pm on Thursday, September 25th, 2008
Can anybody tell me how to write sip programs using perl?
Navin	Posted at 4:00pm on Thursday, October 2nd, 2008
Asthon.. use the below code to get the server up and running in background.. while( $new_sock = $sock->accept()) { while() { print $_; } } close($sock);
Navin	Posted at 4:02pm on Thursday, October 2nd, 2008
while( $new_sock = $sock->accept()) { while() { print $_; } }
Navin	Posted at 4:05pm on Thursday, October 2nd, 2008
looks like .. need to use the escape char to print angle brackets .. inside while should be .. while() {print $_; }
hell	Posted at 4:08pm on Thursday, October 2nd, 2008
while(<$new_sock>) {print $_; }
RRN	Posted at 11:18pm on Monday, November 10th, 2008
can any one help me i am not able to transfer message from one ip to another ip here is the server ################# #!/usr/bin/perl use IO::Socket; my $sock = new IO::Socket::INET ( LocalHost => 'localhost', LocalPort => '7070', Proto => 'tcp', Listen => 1, Reuse => 1, Blocking=>1, ); die "Could not create socket: $!n" unless $sock; my $new_sock = $sock->accept(); while() { print $_; } close($sock); .................. And here is the client ########### #!/usr/bin/perl use IO::Socket; my $sock=new IO::Socket::INET ( PeerAddr=>'localhost', PeerPort=>'7070', Proto=>'tcp', ); die"couldnot create a socket:$!n" unless $sock; foreach my $i (1..5) { print $sock"helloworldn"; } close($sock);
RRN	Posted at 2:15am on Friday, November 21st, 2008
how to block a perticular port using perl in TCP/IP networking
Thanos	Posted at 5:22am on Wednesday, January 28th, 2009
I am trying to build a tcp/ip to serial redirect (both ways) for interfacing with an old control system. I've found somewhere on the net this script http://www.jrbtech.com/2008/code/perl-a-tcp-daemon-written-for-perl.html but does not seem to work as expected. Can anyone help please?
Dave Mathews	Posted at 4:24pm on Sunday, February 8th, 2009
When I send large records from the Client to the Server and write them to a file the records get truncated. In C I had to have the server do multiple receives to get all the data from a single send on the client. How do I do this in Perl?
Kesh	Posted at 1:54am on Tuesday, February 10th, 2009
Great article; thanks.
Minok	Posted at 6:06pm on Thursday, February 12th, 2009
Now, can someone explain why, taking that very basic starting example, if I tweek it to try and create a udp datagram socket, the new fails? my $sock = new IO::Socket::INET ( LocalHost => 'localhost', LocalPort => '1217', Proto => 'udp', Listen => 1, Reuse => 1, Type => SOCK_DGRAM, );
akshatha	Posted at 9:29pm on Sunday, February 15th, 2009
i wanted to have a socket programming using SSH.can we have it?i have got to include a script in that which includes multiple IP adresses.
akshatha	Posted at 9:30pm on Sunday, February 15th, 2009
i wanted to have a socket programming using SSH.can we have it?i have got to include a script in that which includes multiple IP adresses.
Phanleson	Posted at 10:22pm on Friday, February 27th, 2009
Oh, this tutorial is very basic for newbie, i am a java developer and i have learned perl few year ago. Thank you for this tutorial
SS	Posted at 2:33am on Monday, March 2nd, 2009
Develop a application over UDP · Client sends array X and Y to Proxy Server. · Proxy Server receives the two arrays from Client and sends to Server1, Server2 and Server3. · Server1 receives the two arrays from Proxy Server and calculate sum of number and send result to Proxy Server and also print the result on its standard output. · Server2 receives the two arrays from Proxy Server and calculate sum of square and send result to Proxy Server and also prints the result on its standard output. · Server3 receives the two arrays from Proxy Server and calculate sum of cube and send result to Proxy Server and also prints the result on its standard output. · After receiving result from Servers, Proxy Server sends all result to Client. · Proxy Server receiving all results from Servers, it sends to Client.
priya	Posted at 9:15pm on Monday, April 20th, 2009
i want info @ 'select' structure using tcp for messenger
Naresh	Posted at 2:43am on Monday, June 15th, 2009
I need to pass the parameters in url and get back the result to the client in url Please suggest. Thanks
damelep	Posted at 11:50am on Wednesday, June 24th, 2009
Nice work dude ! Excellent Code !!!
Amy	Posted at 10:42am on Wednesday, September 9th, 2009
An awesome tutorial with great code... works perfectly! Thank you!
Anonymous	Posted at 12:15am on Friday, November 20th, 2009
the above client program is not working on my windows xp..... pls help me..
Mike Lacey	Posted at 3:30am on Tuesday, December 15th, 2009
Good article, thank you. You may not be aware that "Network Programming in Perl" at http://home.t-online.de/home/wahls/perlnet.html does not seem to be available anymore. Regards, Mike
Phil	Posted at 7:44am on Wednesday, January 13th, 2010
first Comment in 2010!
Hakim	Posted at 9:13pm on Thursday, January 21st, 2010
I have following perl script whihc runs well on my machine but my other machine is configured in a way where it has to go through a proxy before connecting to those servers. The Proxy IP is "aa.bb.cc.dd" and port is "abcd". How do i script in perl to connect to the servers through proxy servers? Please help!!! use Net::Telnet; $username=hakim; $password=pwd; @server=("ABC","XYZ"); foreach $server (@server){ $telnet = new Net::Telnet (Timeout=>1000,Errmode=>'die',Cmd_remove_mode=>'auto'); $telnet->open($server); $telnet->waitfor('/login: $/i'); $telnet->print($username); $telnet->waitfor('/password: $/i'); $telnet->print($password); $telnet->waitfor('/$ $/i'); $telnet->cmd("cd $HOME"); $telnet->print('find /Path -name "file*" -print 2>/dev/null \| xargs egrep -i "HOST>20100113 $HOME/searchfile'); $telnet->waitfor('/$ $/i'); $telnet->close; }
SydneyBoy	Posted at 8:53pm on Wednesday, March 17th, 2010
Can someone help me for a perl script to limit the internet download size in a LAN based on week
Tekle	Posted at 7:06pm on Thursday, March 25th, 2010
this is a very good introduction.thank you
Dale	Posted at 10:21am on Thursday, April 1st, 2010
How does the client recv a pass back from the Server? I can send to the server no problem and have the server print what I send but if the server send a message back I can seem to get it.
Navnit	Posted at 7:39am on Thursday, April 8th, 2010
Help me please... The following is the out from my terminal when i run the perl script. Can anybody help me? Thanks in advance... ============================================================ Terminal snapshot : ============================================================ [koha@localhost ~]$ cat receiver.pl use IO::Socket; my $sock = new IO::Socket::INET ( LocalHost => 'localhost', LocalPort => '7070', Proto => 'tcp', Listen => 1, Reuse => 1, ); die "Could not create socket: $!n" unless $sock; my $new_sock = $sock->accept(); while() { print $_; } close($sock);[koha@localhost ~]$ cat sender.pl use IO::Socket; my $sock = new IO::Socket::INET ( PeerAddr => 'localhost', PeerPort => '7070', Proto => 'tcp', ); die "Could not create socket: $!n" unless $sock; print $sock "Hello there!n"; close($sock);[koha@localhost ~]$ perl receiver.pl Could not create socket: Invalid argument [koha@localhost ~]$ ============================================================
Navnit	Posted at 7:43am on Thursday, April 8th, 2010
Help me please... The following is the out from my terminal when i run the perl script. Can anybody help me? Thanks in advance... ============================================================ Terminal snapshot : ============================================================ [koha@localhost ~]$ cat receiver.pl use IO::Socket; my $sock = new IO::Socket::INET ( LocalHost => 'localhost', LocalPort => '7070', Proto => 'tcp', Listen => 1, Reuse => 1, ); die "Could not create socket: $!n" unless $sock; my $new_sock = $sock->accept(); while() { print $_; } close($sock); [koha@localhost ~]$ cat sender.pl use IO::Socket; my $sock = new IO::Socket::INET ( PeerAddr => 'localhost', PeerPort => '7070', Proto => 'tcp', ); die "Could not create socket: $!n" unless $sock; print $sock "Hello there!n"; close($sock); [koha@localhost ~]$ perl receiver.pl Could not create socket: Invalid argument [koha@localhost ~]$ ============================================================
uturner	Posted at 12:33pm on Tuesday, May 4th, 2010
class example.........encoded with compiled theory.....
Bilal	Posted at 7:46am on Wednesday, May 5th, 2010
I have a perl script for unix which uses a socket to read data from gsm modem connected to com port.I need to convert it to windows.I think most of the script is going to be same except the line which establishes the socket connection. Could someone please help me to know which lines I should change so that it will work on windows. Here is the script #!/usr/bin/perl -w # TRG: Perl script to exercise GSM card through a set of diagnostic commands # The results from each command are sent back to the browser client # Accesses the GSM card via gsmd socket (for sharing) use strict; use IO::Socket::UNIX; use Term::ReadKey; use IO::Select; use CGI qw(:standard); use CGI::Carp qw(fatalsToBrowser); # Keep Apache happy with the content print "Content-type: text/htmlnn"; # Open the socket connection to GSMD my $sock = new IO::Socket::UNIX (Type => SOCK_STREAM, Peer => '/home/glucose/gsm/gsmd_sock', Timeout => 60) \|\| die "Couldn't establish socket: $!"; $! = 1; my $s = IO::Select->new(); $s->add($sock); $sock->autoflush(1); ReadMode 4; # Display suitable HTML headers and send a series of commands #print "GSM Card Diagnosticsn"; sendcommand($s,$sock,"at+cerrn",'Last Error Message',''); sendcommand($s,$sock,"at+cscs="GSM"n",'Select ASCII output',''); print "GSM Card Detailsn"; sendcommand($s,$sock,"at+cgmin",'Manufacturer Indentification',''); sendcommand($s,$sock,"at+cgmmn",'Model Identification',''); sendcommand($s,$sock,"at+cgmrn",'Revision',''); sendcommand($s,$sock,"at+cgsnn",'Serial Number',''); print "Subscriber Identificationn"; sendcommand($s,$sock,"at+cimin",'International Mobile Subscriber Identity',''); sendcommand($s,$sock,"at+ccidn",'SIM card ID',''); sendcommand($s,$sock,"at+gcapn",'List of capabilities',''); sendcommand($s,$sock,"at+cnumn",'Subscriber number',''); printf "Current Statusn"; sendcommand($s,$sock,"at+cpasn",'Status','(0=ready, 1=unavailable, 2=unknowm, 3=ringing, 4=call-in-progress, 5=asleep'); sendcommand($s,$sock,"at+cfun?n",'Functions','(power,stk)'); sendcommand($s,$sock,"at+cmer?n",'Term event reporting','(mode,kpd,disp,ind,bfr)'); sendcommand($s,$sock,"at+cclk?n",'clock','(yy/mm/dd hh:mm:ss)'); sendcommand($s,$sock,"at+csqn", 'Signal Strength','(rssi,ber)'); sendcommand($s,$sock,"at+creg?n",'Network registration ','(n,stat,location,cellident) stat=1(home) '); printf "SMSn"; sendcommand($s,$sock,"at+cnmi?n",'New Message Indication'); sendcommand($s,$sock,"at+csca?n",'Service centre address'); sendcommand($s,$sock,"at+cmgln",'List messages'); sendcommand($s,$sock,"at+cscs="HEX"n",'Hex output',''); # Close the socket connection and were done $sock->close(); ReadMode 0; exit; # ----------------------------------------------------------------- # Subroutine to send a command to the diagnostic socket and print the response sub sendcommand { my $s = shift; my $sock = shift; my $cmd = shift; my $desc = shift; my $comment = shift; my $rtn = ''; #print description print "$desc "; #send the command $sock->syswrite($cmd); sleep 1; # read the response and print while ($s->can_read(0)) { $sock->sysread($rtn,1); print $rtn; } print "n $commentn"; return; }
machchakumar	Posted at 12:28am on Wednesday, June 23rd, 2010
it is usfull for me because read about more for tcp/ip ,socket,ect
Harpreet	Posted at 9:45pm on Thursday, July 29th, 2010
Thanks, created a script using the above... http://rowsandcolumns.blogspot.com/2010/07/perl-how-to-create-tcp-socket.html
thangavel	Posted at 4:24am on Wednesday, October 20th, 2010
super thought
lordcountley@gmail.com	Posted at 5:09am on Sunday, November 7th, 2010
very good
Super_carotte	Posted at 8:35am on Thursday, November 25th, 2010
To Bilal: have you tried this line at the end of your code: $SIG{CHLD} = 'IGNORE';
Craig	Posted at 9:03pm on Sunday, December 19th, 2010
I have struggled with writing a stand alone SMTP Mail Server in Perl for years. NETSMTP doesn't cut it for me and I've bought fancy junk that doesn't give me the control or simplicity I wanted. Your script did. I am not done yet - my GNUSMTP.PL sends messages but the message body is empty (?hmmmm) - but for the first time ever I can actually get a message sent from a file to yahoo or gmail and that's a first step.
Craig	Posted at 9:04pm on Sunday, December 19th, 2010
I have struggled with writing a stand alone SMTP Mail Server in Perl for years. NETSMTP doesn't cut it for me and I've bought fancy junk that doesn't give me the control or simplicity I wanted. Your script did. I am not done yet - my GNUSMTP.PL sends messages but the message body is empty (?hmmmm) - but for the first time ever I can actually get a message sent from a file to yahoo or gmail and that's a first step.
Ijalba	Posted at 8:41am on Thursday, January 13th, 2011
First comment of 2011, hehehe. I get an error on the 1st script: "use" not allowed in expression at opensocket.pl line 21, at end of line syntax error at opensocket.pl line 21, near "use IO::Socket"
Ijalba	Posted at 9:41am on Thursday, January 13th, 2011
Corrected. It works FINE!!!! very good example. It will aid me greatly to test connections properly without having to depend on external applications, or in the network guys...
Natali	Posted at 5:11am on Monday, January 31st, 2011
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Gururaj CM	Posted at 9:52pm on Monday, February 14th, 2011
Thanks really it was a great material
rocko	Posted at 6:37pm on Sunday, March 27th, 2011
Can localhost =>"" be any PC's IP address? I have 2 PC's on my home network and would like to try this script on them. But I keep getting:"Cannot create socket, Cannot assign address", when ever I put anything other then the localhost address.
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Ankur	Posted at 12:13am on Thursday, April 14th, 2011
Is there any way we can do the client server communication using MAC address instead of IP address. i.e. using LLC protocol instead of TCP/UDP
petros	Posted at 11:08am on Sunday, May 8th, 2011
are you from Cyrpus or greecy? Awesome article really helpfull :D
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Thanks from Paris
YAK3	Posted at 8:56am on Tuesday, May 31st, 2011
This article helps me!! thanks!! :)
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Xhesi	Posted at 6:56pm on Friday, June 24th, 2011
Great for beginners! Thanks a lot! :)
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Suresh	Posted at 11:29pm on Tuesday, July 5th, 2011
Good to practice
shan singh	Posted at 10:32am on Tuesday, September 27th, 2011
i cannot create a socket form caller side. please help soon
shan singh	Posted at 10:35am on Tuesday, September 27th, 2011
i cannot create a socket form caller side. please help soon
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Charles	Posted at 11:10pm on Tuesday, October 4th, 2011
Having an issue with sockets. I connect to the server with my client, then send a request and receive a response. I'm then parsing the response with XML::XPath. This works perfectly fine the first time through. However, if I send another transaction with the same socket and receive another response, XML::XPath cannot parse the response, even though it just appears to be a regular xml string. If I close the socket and open a new one and do it all over again, it works fine. But I don't want to be opening and closing the socket each time, I want to make all of my transactions on the open socket and then close when I'm done. I've set autoflush to 1, but that made no difference. What am I missing? Charles
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Parag Kamble	Posted at 11:18pm on Monday, December 5th, 2011
How to transfer File Using Socket?
Imran Saad	Posted at 6:27am on Monday, December 12th, 2011
A socket can be created with a SIP server on port 5060 but what protocol should be used to supply username and password to get registered to the SIP server . NAT has to be disabled for SIP to work well because of address mismatch issues . A perl script to check if client is registered to SIP Server which means check registration status of a particular user/password combination .,
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therulerofchina	Posted at 1:52pm on Tuesday, February 21st, 2012
is it possible to use this to execute commands as well or is it just talk? i tried replacing print with system ($^X, $_) but that didn't work.... otherwise a brilliant tutorial!
Nima	Posted at 1:01am on Tuesday, March 6th, 2012
Excellent job! You really made it easy for us to understand the concept of socket...Thank you.
Anonymous	Posted at 9:37pm on Wednesday, March 14th, 2012
thanks sir G ur notes is well
Richard Braganza	Posted at 5:57am on Tuesday, April 17th, 2012
Thanks for this but should not Listen should close $newsock and not $sock R
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Senad	Posted at 11:33pm on Monday, August 20th, 2012
There really isn't a huge avadntage to using sockets. My tests with a clean install of WordPress 3.0 with no plugins and running Twentyten showed negligible speed improvements. Using localhost I averaged 0.2103 seconds for 15 queries (over 20 tests) and with sockets I averaged 0.20965 seconds for 15 queries (over 20 tests). This is generally just required due to server configs. Why all of the sudden users are needing this? I couldn't say; maybe it is just the latest MySQL configuration craze ;)
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Shaheed	Posted at 12:00am on Tuesday, January 22nd, 2013
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Comments to date: 147.