So I have this problem while looping through a socket with a while loop.
When I use this, it totally works fine but I have newlines on every $message, which I don't want.
my $socket = new IO::Socket::INET (
LocalHost => "127.0.0.1",
LocalPort => "12345",
Proto => 'tcp',
Listen => 1,
Reuse => 1
);
my $client = $socket->accept();
while(<$client>) {
my $message = $_;
print $message;
}
But when I add the chomp the loop only finished when I disconnect the client (which I understand why).
My guess is that chomp removes the newline from the $_ variable and thus the loop will not work anymore.
my $socket = new IO::Socket::INET (
LocalHost => "127.0.0.1",
LocalPort => "12345",
Proto => 'tcp',
Listen => 1,
Reuse => 1
);
my $client = $socket->accept();
while(<$client>) {
my $message = $_;
chomp($message);
print $message;
}
So my question is: How can I loop through the socket (newline terminated) without having the newlines in the messages?
Thanks a bunch!
The chomp is made on a copy of $_, so it should not affect the socket handle at all. More likely, the removal of the newline is making your print statement wait in the buffer, and execute once the script is terminated.
In other words: It's not an error, just a delay.
Try using autoflush to execute the print immediately.
$| = 1;
Related
I want to set timeout in my recv function in this specific code below, because sometimes my script stuck forever. I am new in socket programming so i would really appreciate any help. Thanks in advance.
use IO::Socket::INET;
use IO::Select;
use LWP::UserAgent;
use JSON::XS 'decode_json';
use Data::Dumper;
use DBI();
sub dbconn {
my $db_conf = shift;
my $dbh = DBI->connect("DBI:Pg:dbname=somedatabase;host=somehost", "postgres", "",
{pg_server_prepare =>
0,AutoCommit => 1,RaiseError=>1});
$dbh->do("SET CLIENT_ENCODING TO 'UTF-8';");
return $dbh;
}
# auto-flush on socket
$| = 1;
# creating a listening socket
my $socket = new IO::Socket::INET (
LocalHost => '0.0.0.0',
LocalPort => '5000',
Proto => 'tcp',
Listen => 5,
Reuse => 1
);
die "cannot create socket $!\n" unless $socket;
$sel = IO::Select->new( $socket );
print "Server waiting for client connection on port 5000...\n";
my $command = 1;
my $watchTracker = "*HQ,";
my $tl206 = ",LAT:";
my $watchConnectedCheck = ",A,";
my $gpsType;
my $circleString = ",LINK,";
my $dataToSend;
my $new;
my $dbh = dbconn();
while(#ready = $sel->can_read) {
foreach $fh (#ready) {
if($fh == $socket) {
# Create a new socket
$new = $socket->accept;
$new->recv($dataReceived, 1024);
$new->recv($dataReceived, 1024);
# get information about a newly connected client
my $client_address = $new->peerhost();
my $client_port = $new->peerport();
print "===============================================\n";
print "===============================================\n\n";
print "Connection from $client_address:$client_port\n";
print "General data received: $dataReceived\n\n";
#MORE LINES...
}
else {
# Process socket
# Maybe we have finished with the socket
$sel->remove($fh);
$fh->close;
}
}
}
$dbh->disconnect();
Perhaps I am misunderstanding the question, but have you tried setting a timeout in the socket with "Timeout"?
See IO::Socket::INET.
EDIT: I did not catch the 'recv' bit. You have to use setsockopt, which is not wholly portable, so the final answer is somewhat dependent on your platform. Here are some posts that may help:
How do I set `SO_RCVTIMEO` on a socket in Perl?
http://www.perlmonks.org/?node_id=761935
E.g.,
$socket->setsockopt(SOL_SOCKET, SO_RCVTIMEO, pack('l!l!', 30, 0))
or die "setsockopt: $!";
use strict; use warnings;
use IO::Socket;
use IO::Select;
my $read_select = IO::Select->new();
my $write_select = IO::Select->new();
my $socket = IO::Socket::INET->new(
LocalHost => '127.0.0.1',
LocalPort => '5556',
Proto => 'tcp',
Listen => 50,
Reuse => 1,
) or die "Could not create socket: $!";
print "Socket Created . Waiting for connection ...\n";
## poll to accept new connection or to receive data from a connection
$read_select->add($socket);
print "Added socket to read list ";
my $reade;
my $newconn;
my #read;
my #write;
while(1) {
#read = $read_select->can_read();
foreach my $reade(#read) {
if($reade == $socket) {
print "New conn received";
my $newconn = $reade->accept();
$write_select->add($newconn);
}
else {
print "data received";
}
}
}
#write = $write_select->can_write();
foreach my $write(#write) {
$write->send("got ur data");
}
I am trying to poll for connections using select statement. Why is that if i use an infinite loop, no connection is accepted. It works fine without while(1)
I think you are being bitten by I/O buffering here. Perl buffers all input and output. It generally doesn't print to the terminal until it has received an entire line.
Your code is probably working with the while(1), but you can't see the output of your debug print statements because the output to the terminal is being buffered. Once you get to the second time through the loop, $read_select->can_read() blocks forever, so you never see the output of the print statements.
You can probably fix this just by adding \n to the end of each print statement. Another option is setting $| = 1;. This disables buffering. See perlvar's discussion of $| for more information on buffering.
This is my current code:
#!/usr/bin/perl -w
use strict;
require IO::Socket;
while (<>) {
chomp(my $host = $_);
my #header;
print "Connecting to: $host\n";
my $socket = new IO::Socket::INET(
PeerAddr => $host,
PeerPort => 80,
Proto => 'tcp') || print "Could not connect: $!\n";
print "Connected.\n";
print $socket "GET / HTTP/1.0\n\n";
my $i = 0;
while (<$socket>) {
#header[$i] = $_;
$i++;
}
$i = 0;
print "--------------------------------------\n";
while ($i <= 8) {
print "#header[$i++]";
}
print "-------------------------------------\n";
print "Finished $host\n\n";
}
If while going through a list of IP's, and a host is down, instead of continuing onto the next IP, it will give me an error "Can't use string ("1") as a symbol ref while "strict refs" in use".
If I then change #header[$i] = $; to $header[$i] = $; I also get the same error. How can I make this script better.
The problem is in the way you set $socket:
my $socket = new IO::Socket::INET(
PeerAddr => $host,
PeerPort => 80,
Proto => 'tcp') || print "Could not connect: $!\n";
Since you're using the || operator, which has higher precedence than =, this statement is parsed as
my $socket = (new IO::Socket::INET(...) || print ...);
If new IO::Socket::INET returns a false value (as it does if the connection fails), the print will be executed and its return value (which is normally 1) will be assigned to $socket.
When you then try to use $socket as an indirect object in the statement:
print $socket "GET / HTTP/1.0\n\n";
Perl notices that the value 1 is not actually an object reference and throws the error you reported.
If you'd used the low-precedence operator or instead of ||, the value of $socket would've been undef instead of 1, and the error message you'd have received would've been something like Can't use an undefined value as a symbol reference .... Of course, this wouldn't have actually fixed your problem, but at least it might've made it easier to diagnose.
To actually fix the problem, you need to fix your code so that you won't keep executing the rest of the loop body if the connection fails. One way to do that would be like this:
my $socket = new IO::Socket::INET(
PeerAddr => $host,
PeerPort => 80,
Proto => 'tcp');
unless ($socket) {
print "Could not connect: $!\n";
next; # skip the rest of the loop
}
Wouldn't the simple solution be to use the lower precedence version 'or' which has lower precedence than '='?
my $socket = new IO::Socket::INET(
PeerAddr => $host,
PeerPort => 80,
Proto => 'tcp')
or print "Could not connect: $!\n";
In fact, the operators 'or', and 'xor', have the lowest operator precedence (see perlop).
I am trying to write a simple IO::Socket connection in perl. However, I am running into some problems. Here is the code on the server side:
my $listener =
IO::Socket::INET->new( LocalPort => 8000, Listen => 1, Reuse => 1 );
die "Can't create socket for listening: $!" unless $listener;
print "Listening for connections on port 8000\n";
while(1) {
while ($client = $listener->accept()) {
while ( <$client>) {
my #arguments = split(/ /, $_ );
my $result = "something" ;# here we do something in my code
warn $result;
print $client $result;
close $client;
}
}
}
And the client code:
use IO::Socket;
my $sock = new IO::Socket::INET (
PeerAddr => 'xx.xxx.xxx.xxx',
PeerPort => '8000',
Proto => 'tcp',
);
die "Could not create socket: $!\n" unless $sock;
$sock->autoflush(1);
print $sock "somethin something";
print "sent\n";
while ( <$sock> ) { print }
close $sock;
My problem now is that the data seems to be only sent from the client to teh sever when I close the client Perl program. I get the "sent" message on the client side, but the "something" message on the server side does not appear until after I have manually closed the client side.
Also, I want to get the server response. Thus far, since I have to close the script manually, the response does not et to the client side.
Can anyone help?
while ( <$sock> ) -- waits for a line. That is for a string, ended by "\n" character.
You must add "\n" to strings, or use 'read' function instead.
here is the request URL http://localhost:9009/?comd&user=kkc&mail=kkc#kkc.com
what are the modification need to do in the server perl script.
server-Perl-script
use IO::Socket;
use Net::hostent; # for OO version of gethostbyaddr
$PORT = 9009; # pick something not in use
$server = IO::Socket::INET->new( Proto => 'tcp',
LocalPort => $PORT,
Listen => SOMAXCONN,
Reuse => 1);
die "can't setup server" unless $server;
print "[Server $0 accepting clients]\n";
while ($client = $server->accept())
{
$client->autoflush(1);
print $client "Welcome to $0; type help for command list.\n";
$hostinfo = gethostbyaddr($client->peeraddr);
printf "[Connect from %s]\n", $hostinfo ? $hostinfo->name : $client->peerhost;
print $client "Command? ";
while ( <$client>) {
next unless /\S/; # blank line
if (/comd/i ) { print $client `dir`; }
} continue {
print $client "Command? ";
}
close $client;
print "client closed";
}
I assume that your script is not for production, but for homework or testing sometime. There are multiple very efficient web server solutions in/with Perl like Apache with CGIs or mod_perl, HTTP::Server::Simple and PSGI/Plack.
You'll also typically use a framework like Dancer, Mojo or Catalyst which does most of the boring standard stuff for you:
use Dancer;
get '/' => sub {
return 'Hi there, you just visited host '.request->host.
' at port '.request->port.' asking for '.request->uri;
};
Back to your question: Your script is a interactive server while HTTP has a strict request and response structure:
Client connects to server
Client sends a request
Server sends a response
You need to remove the interactive part and just wait for the client to start the conversation:
use IO::Socket;
use Net::hostent; # for OO version of gethostbyaddr
$PORT = 9009; # pick something not in use
$server = IO::Socket::INET->new( Proto => 'tcp',
LocalPort => $PORT,
Listen => SOMAXCONN,
Reuse => 1);
die "can't setup server" unless $server;
print "[Server $0 accepting clients]\n";
while ($client = $server->accept())
{
$hostinfo = gethostbyaddr($client->peeraddr);
# Read request up to a empty line
my $request;
while ( <$client>) {
last unless /\S/;
$request .= $_;
}
# Do something with the request
# Send response
print $client "Status: 200 OK\r\nContent-type: text/plain\r\n\r\n".$request;
close $client;
print "client closed";
}
The server reads the full request from the client and returns a minimized HTTP header plus the original request.