English
English
[getservbyname and getservbyport: Differences and Appropriate Use Cases]
In PHP, getservbyname and getservbyport are two functions related to network programming. They are used to retrieve the mapping between service names and port numbers, providing developers with a convenient way to query information when dealing with network communication. Although similar in function, their usage scenarios and parameter requirements differ.
The getservbyname function is used to obtain the port number corresponding to a service name. Its basic syntax is as follows:
<span><span><span class="hljs-title function_ invoke__">getservbyname</span></span><span>(</span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$service</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$protocol</span></span><span>): </span><span><span class="hljs-keyword">string</span></span><span>|</span><span><span class="hljs-literal">false</span></span><span>
</span></span>$service: The name of the service, such as "http", "ftp", or "smtp".
$protocol: The protocol type, usually "tcp" or "udp", specifying the protocol the service uses.
This function returns the port number corresponding to the service name or false if not found.
In contrast to getservbyname, the getservbyport function retrieves the service name corresponding to a port number. Its basic syntax is:
<span><span><span class="hljs-title function_ invoke__">getservbyport</span></span><span>(</span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$port</span></span><span>, </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$protocol</span></span><span>): </span><span><span class="hljs-keyword">string</span></span><span>|</span><span><span class="hljs-literal">false</span></span><span>
</span></span>$port: The port number, usually an integer (e.g., 80, 443, 21).
$protocol: The protocol type, typically "tcp" or "udp".
This function returns the service name corresponding to the port number or false if not found.
Although both getservbyname and getservbyport query the mapping between services and ports, their main difference lies in the starting point of the query:
Query Method:
getservbyname looks up the port number by service name.
getservbyport looks up the service name by port number.
Use Cases:
Use getservbyname when you know the service name (like HTTP, FTP) but need to find its port number.
Use getservbyport when you know the port number (like 80, 443) but want to identify which service uses it.
Return Values:
getservbyname returns the port number.
getservbyport returns the service name.
Identify the port used by a service:
If you are developing a network service, you may need to query the port number corresponding to a service name. For instance, when developing a web application, you may want to confirm the port for the HTTP service (usually 80) or HTTPS (usually 443). In this case, getservbyname is appropriate.
Example code:
<span><span><span class="hljs-variable">$port</span></span><span> = </span><span><span class="hljs-title function_ invoke__">getservbyname</span></span><span>(</span><span><span class="hljs-string">'http'</span></span><span>, </span><span><span class="hljs-string">'tcp'</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"HTTP service port is: <span class="hljs-subst">$port</span>";</span></span>Network application port configuration:
When writing code related to network protocols, you may need the port number for socket binding or communication setup. In this scenario, getservbyname provides the port information efficiently.
Look up a service by port number:
During network troubleshooting or security audits, you may only know the port number but not the service. Here, getservbyport helps identify the service using that port.
Example code:
<span><span><span class="hljs-variable">$service</span></span><span> = </span><span><span class="hljs-title function_ invoke__">getservbyport</span></span><span>(</span><span><span class="hljs-number">80</span></span><span>, </span><span><span class="hljs-string">'tcp'</span></span><span>);
</span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"Port 80 corresponds to service: <span class="hljs-subst">$service</span>";</span></span>Handle port-to-service mappings:
If you are developing a network monitoring tool or firewall configuration tool, you may need to determine the service corresponding to a port number for rule settings or service identification. In this case, getservbyport is very useful.
getservbyname and getservbyport are both useful for managing network services and port relationships. Choosing the right function helps developers efficiently manage services and debug networks:
Use getservbyname when the service name is known and you need the port.
Use getservbyport when the port number is known and you want to find the service using it.
The key difference between these two functions lies in the starting point of the query and the returned result. Developers should choose based on specific requirements.
