Introduction:
If you want to know what are all the ports opened in your system and which are all the ports blocked by firewall, then this link may helpful for you.
What is Firewall?
In computing, a firewall is a network security system that monitors and controls the incoming and outgoing network traffic based on predetermined security rules. A firewall typically establishes a barrier between a trusted, secure internal network and another outside network, such as the Internet, that is assumed not to be secure or trusted. Firewalls are often categorized as either network firewalls or host-based firewalls.
What is a Network Port?
A network port is a process-specific or an application-specific software construct serving as a communication endpoint, which is used by the Transport Layer protocols of Internet Protocol suite, such as User Diagram Protocol (UDP) and Transmission Control Protocol (TCP)
Available Port with Number Details:
![table]()
Click this URL to check the port availability.
Where is this used for me?
When you develop an application and the application tries to communicate with any other application internal or external then it communicates through the appropriate port and due to security issues and firewalls available in your anti-virus can block some of the port.
Where there will be communication error mostly of “Access Denied” or “Error - 404”, so during that time there is nothing to do with your code, just check the proper communications are happening properly and no blockage of ports for easy, quick and better work arounds.
Question:
SMTP [Mail Sending service] is configured in my system and yet I am not able to send mail?
Answer:
The SMTP port may be blocked in your system. [This can be checked using above URL - Port No. 25 for SMTP]
Command used in Windows Command Prompt:
Telnet Format
C: \> telnet IP-address Port- Number
Example
C: \> telnet 10.131.134.87 25
If the error is shown the port is blocked, if you see a blank screen then the port is opened.
Thanks.