The getservbyname() function returns the port number of a specified service.

Prototype:

int getservbyname(string service, string protocol)

Example:

<?php
   echo "HTTP's default port number is: ".getservbyname("http","tcp");

?>

The fsocketopen() function establishes a connection to the resource designated by target on port.

Prototype:

resource fsockopen( string target, int port [, int erron [, string errsting [, float timeout]]])

Example:

<?php
   $http=fsockopen("www.example.com",80);
  
   $req="GET / HTTP/1.1\r\n";
   $req.="Host: www.example.com\r\n";
   $req.="Connection: Close\r\n\r\n";

  fputs($http,$req);
 
  while(!feof($http)){

      echo fgets($http,1024);

   }
fclose($http);
 
?>

Directory Service: It offers system administrators, developers, and end users alike a consistent, efficient, and secure means for viewing and managing resources such as people, fles, printers, and applications.

The ldap_connect() function establishes a connection to an LDAP server identified by a specific host name and optionally a port number.

Prototype:

resource ldap_connect([stiring hostname[, int port]])

Example:

<?php
   $host="ldap.wjgilmore.com";
   $post="389";
   $connection=ldap_connect($host,$port) ro die("Can't establish LDAP connection");
?>

Web service: Web services are typically application programming interfaces (APIs) or web APIs that are accessed via Hypertext Transfer Protocol (HTTP) and executed on a remote system hosting the requested services.