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    <h1>Revised Edition of Answer</h1> <p>This code includes 3 scripts:</p> <ol> <li><code>serverJ.pl</code> which is an iterative server, processing one request at a time, but continuing to process multiple requests;</li> <li><code>clientJ.pl</code> which is a simple client that sends the login request from the <code>Login.txt</code> file and echoes what it receives from the server; and</li> <li><code>clientQ.pl</code> which sends a QUIT message to the server.</li> </ol> <p>I've left the code using old-fashioned file handles rather than upgrading to modern lexical file handles, but I changed to the 3-argument form of <code>open</code>. One other change is that most messages are prefixed with <code>$$:</code>, the Perl process ID. I would not have labelled the <code>INNER:</code> loop except for symmetry with the <code>OUTER:</code> loop, which does need a label. It is not clear that the functions <code>send_login()</code> and <code>abc()</code> are needed in <code>clientJ.pl</code>; they are left in deference to the original code.</p> <h3>serverJ.pl</h3> <pre><code>#!/usr/bin/env perl use strict; use warnings; use IO::Socket::INET; my $socket = new IO::Socket::INET ( LocalHost =&gt; '127.0.0.1', LocalPort =&gt; '1055', Proto =&gt; 'tcp', Listen =&gt; 1, Reuse =&gt; 1 ) or die "Oops: $! \n"; print "$$: waiting for clients.\n"; server_loop(); $socket-&gt;close(); sub server_loop { OUTER: while (my $clientsocket = $socket-&gt;accept()) { print "$$: connected from : ", $clientsocket-&gt;peerhost(); print ", port : ", $clientsocket-&gt;peerport(), "\n"; INNER: while (&lt;$clientsocket&gt;) { print"$$: Message received from Client : $_"; last INNER if ($_ eq "\$END\$\n"); last OUTER if ($_ eq "\$QUIT\$\n"); print $clientsocket $_; } my $login_ack = "login_ack.txt"; open LOGINACK, '&lt;', $login_ack or die "Cannot open login acknowledgment file $login_ack ($!)\n"; my @loginack = &lt;LOGINACK&gt;; close LOGINACK; my $logfile = "logfile.txt"; open LOG, "&gt;&gt;", $logfile or die "$$: cannot open $logfile ($!)\n"; foreach my $loginack (@loginack) { last if ($loginack eq "\$END\$\n"); print $clientsocket $loginack; print LOG "$$: $loginack"; print "$$: server to client: $loginack"; } close LOG; close $clientsocket; } } </code></pre> <h3>clientJ.pl</h3> <pre><code>#!/usr/bin/env perl use strict; use warnings; use IO::Socket::INET; my $socket = new IO::Socket::INET ( PeerHost =&gt; '127.0.0.1', PeerPort =&gt; '1055', Proto =&gt; 'tcp', Reuse =&gt; 1 ) or die "$!\n"; print "$$: connected to the server.\n"; send_login(); abc(); $socket-&gt;close(); sub send_login { my $login_txt = "Login.txt"; open LOGIN, '&lt;', $login_txt or die "Cannot open $login_txt $!\n"; my @login = &lt;LOGIN&gt;; close LOGIN; my $logfile = "logfile.txt"; open LOG, '&gt;&gt;', $logfile or die "Cannot open $logfile ($!)\n"; foreach my $login (@login) { print $socket $login; print LOG "$$: $login"; print "$$: sent to server: $login"; last if ($login eq "\$END\$\n"); } close LOG; } sub abc { while (&lt;$socket&gt;) { print"$$: Message received from Server: $_"; } } </code></pre> <h3>clientQ.pl</h3> <pre><code>#!/usr/bin/env perl use strict; use warnings; use IO::Socket::INET; my $socket = new IO::Socket::INET( PeerHost =&gt; '127.0.0.1', PeerPort =&gt; '1055', Proto =&gt; 'tcp', Reuse =&gt; 1 ) or die "$!\n"; print $socket "\$QUIT\$\n"; $socket-&gt;close(); </code></pre> <h3>Sample log</h3> <pre><code>$ perl serverJ.pl 2&gt;&amp;1 &amp; [1] 87610 $ 87610: waiting for clients. $ perl clientJ.pl | so 87610: connected from : 127.0.0.1, port : 57143 87610: Message received from Client : SAS4 87610: Message received from Client : 50 87610: Message received from Client : SAS_ACTION LOGIN 87610: Message received from Client : LOGIN bss 87610: Message received from Client : PASSWORD cleint 87610: Message received from Client : $END$ 87610: server to client: SAS4 87610: server to client: 61 87610: server to client: SAS_ACTION LOGIN_ACK 87610: server to client: ACK_STATUS 0 87610: server to client: ACK_MESSAGE Logged In 87614: connected to the server. 87614: sent to server: SAS4 87614: sent to server: 50 87614: sent to server: SAS_ACTION LOGIN 87614: sent to server: LOGIN bss 87614: sent to server: PASSWORD cleint 87614: sent to server: $END$ 87614: Message received from Server: SAS4 87614: Message received from Server: 50 87614: Message received from Server: SAS_ACTION LOGIN 87614: Message received from Server: LOGIN bss 87614: Message received from Server: PASSWORD cleint 87614: Message received from Server: SAS4 87614: Message received from Server: 61 87614: Message received from Server: SAS_ACTION LOGIN_ACK 87614: Message received from Server: ACK_STATUS 0 87614: Message received from Server: ACK_MESSAGE Logged In $ perl clientJ.pl | so 87610: connected from : 127.0.0.1, port : 57144 87610: Message received from Client : SAS4 87610: Message received from Client : 50 87610: Message received from Client : SAS_ACTION LOGIN 87610: Message received from Client : LOGIN bss 87610: Message received from Client : PASSWORD cleint 87610: Message received from Client : $END$ 87610: server to client: SAS4 87610: server to client: 61 87610: server to client: SAS_ACTION LOGIN_ACK 87610: server to client: ACK_STATUS 0 87610: server to client: ACK_MESSAGE Logged In 87617: connected to the server. 87617: sent to server: SAS4 87617: sent to server: 50 87617: sent to server: SAS_ACTION LOGIN 87617: sent to server: LOGIN bss 87617: sent to server: PASSWORD cleint 87617: sent to server: $END$ 87617: Message received from Server: SAS4 87617: Message received from Server: 50 87617: Message received from Server: SAS_ACTION LOGIN 87617: Message received from Server: LOGIN bss 87617: Message received from Server: PASSWORD cleint 87617: Message received from Server: SAS4 87617: Message received from Server: 61 87617: Message received from Server: SAS_ACTION LOGIN_ACK 87617: Message received from Server: ACK_STATUS 0 87617: Message received from Server: ACK_MESSAGE Logged In $ perl clientQ.pl | so 87610: connected from : 127.0.0.1, port : 57147 87610: Message received from Client : $QUIT$ [1]+ Done perl serverJ.pl 2&gt;&amp;1 $ </code></pre> <hr> <h3>Post loop code executes</h3> <blockquote> <p>In the server script, while sending the acknowledgement, the code after the <code>foreach my $loginack (@loginack)</code> loop does not get executed. I think that is because the code cannot break out of the loop. How shall it be dealt with?</p> </blockquote> <p>Mildly modified code in <code>serverJ.pl</code>:</p> <pre><code> foreach my $loginack (@loginack) { last if ($loginack eq "\$END\$\n"); print $clientsocket $loginack; print LOG "$$: $loginack"; print "$$: server to client: $loginack"; } print "$$: End of Loop\n"; close LOG; close $clientsocket; print "$$: After close\n"; </code></pre> <p>Example run:</p> <pre><code>$ perl serverJ.pl &amp; [1] 6913 $ 6913: waiting for clients. $ perl clientJ.pl 6915: connected to the server. 6913: connected from : 127.0.0.1, port : 52454 6915: sent to server: This is the file Login.txt 6913: Message received from Client : This is the file Login.txt 6915: sent to server: It contains more than 1 line 6915: sent to server: It also contains this one 6915: sent to server: $END$ 6913: Message received from Client : It contains more than 1 line 6913: Message received from Client : It also contains this one 6913: Message received from Client : $END$ 6915: Message received from Server: This is the file Login.txt 6915: Message received from Server: It contains more than 1 line 6915: Message received from Server: It also contains this one 6913: server to client: This is the file login_ack.txt 6913: server to client: As with the other file, it contains multiple lines 6913: server to client: Several of them. 6913: server to client: This is one of them. 6915: Message received from Server: This is the file login_ack.txt 6913: End of Loop 6915: Message received from Server: As with the other file, it contains multiple lines 6915: Message received from Server: Several of them. 6915: Message received from Server: This is one of them. 6913: After close $ perl clientQ.pl 6913: connected from : 127.0.0.1, port : 52455 6913: Message received from Client : $QUIT$ [1]+ Done perl serverJ.pl $ </code></pre> <hr> <h1>Original Edition of Answer</h1> <p>This code seems to work for me (for a loose definition of 'works'). It is closely based on your code, but using socket 1055 instead of 0155 (I run on Unix; I'd have to be root to use a port number less than 1024), and with <code>use strict;</code> and <code>use warnings;</code> and other minor cleanups.</p> <h3>server.pl</h3> <pre><code>#!/usr/bin/env perl use strict; use warnings; use IO::Socket::INET; my $socket = new IO::Socket::INET( LocalHost =&gt; '127.0.0.1', LocalPort =&gt; '1055', Proto =&gt; 'tcp', Listen =&gt; 1, Reuse =&gt; 1 ) or die "Oops: $! \n"; print "Waiting for the Client.\n"; my $clientsocket; while ($clientsocket = $socket-&gt;accept()) { print "Connected from : ", $clientsocket-&gt;peerhost(); print ", Port : ", $clientsocket-&gt;peerport(), "\n"; while (&lt;$clientsocket&gt;) { if ($_ ne "\$END\$\n") { print"Message received from Client : $_"; print $clientsocket $_; } else { print"\$END\$\n"; } } last; } login_ack(); sub login_ack { # Some code removed for the purpose of posting open (LOGINACK, "login_ack.txt") || die "Cannot open login acknowledgment file $!\n"; my @loginack=&lt;LOGINACK&gt;; close LOGINACK; open(LOG, "&gt;&gt;logfile.txt"); foreach my $loginack (@loginack) { if ($loginack ne "\$END\$\n") { print $clientsocket $loginack; print LOG $loginack; print $loginack; } else { print"\$END\$\n"; } } } </code></pre> <h3>client.pl</h3> <pre><code>#!/usr/bin/env perl use strict; use warnings; use IO::Socket::INET; my $socket = new IO::Socket::INET ( PeerHost =&gt; '127.0.0.1', PeerPort =&gt; '1055', Proto =&gt; 'tcp', Reuse =&gt; 1) or die "$!\n"; print "Connected to the Server.\n"; send_login(); sub send_login { # Some code removed for the purpose of posting open (LOGIN, "Login.txt") || die "Cannot open login file $!\n"; my @login=&lt;LOGIN&gt;; close LOGIN; open(LOG, "&gt;&gt;logfile.txt"); foreach my $login (@login) { if ($login ne "\$END\$\n") { print $socket $login; print LOG $login; print $login; } else { print"\$END\$\n"; } } } LOGINACK: while (&lt;$socket&gt;) { print"Message received from Server : $_"; print $socket $_; last LOGINACK; } </code></pre> <h3>Login.txt</h3> <pre><code>This is the content of the Login.txt file. $END$ </code></pre> <h3>login_ack.txt</h3> <pre><code>This is the contents of the login_ack.txt file. It has two lines of text plus the $END$ line. $END$ </code></pre> <h3>Sample output</h3> <pre><code>$ perl server.pl &amp; [1] 74838 $ Waiting for the Client. $ perl client.pl | so Connected from : 127.0.0.1, Port : 51109 Message received from Client : This is the content of the Login.txt file. Message received from Client : This is the content of the Login.txt file. Connected to the Server. This is the content of the Login.txt file. $END$ Message received from Server : This is the content of the Login.txt file. This is the contents of the login_ack.txt file. It has two lines of text plus the $END$ line. $END$ [1]+ Done perl server.pl $ </code></pre> <p>The server terminates after responding to a single request.</p>
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    1. COHey Jon, thanks for having a look at the code, but your variant of th code yields the exact same output as the one ive put up. Like 100pc. Also, regarding the use strict, use warnings, i used it in the actual code, for the purpose of posting it here, the SSCCE thing you taught me, i removed it.
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      1. USSahej Narang
    2. COAn SSCCE is complete; the `use` statements are part of the completeness. People are apt to comment on the absence of `use strict` and `use warnings` so it is best to include them to head off trouble. The shebang line is perhaps optional; I'd include it — as shown.
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    3. COThank You Jonanthan!
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