Incoming Connection Ports (DRPF) Explained

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Dummy users do not worry about how the communication is realized during internet connection. They do not know what  "connection port numbers”, “dynamic RPF”, “open and closed ports” are… But if you are going to use a secure internet connection via VPN, you need to know something about incoming connection ports. When connected to a VPN server, this server automatically becomes a firewall between you and the Internet. And the applications you usually use may not work. Why can it happen?, how to resolve this issue? Read this article…

What are incoming connection ports?

How an application installed on your computer knows where to send data to on Internet? In addition to the IP address of a remote machine, the programs must know the port numbers of the receiving application. Imagine a letter which comes to an address – a building with thousands of rooms.  And to what room must the letter be delivered? So, ports are like room numbers or post office boxes – they specify where exactly the message must be delivered.  Port numbers range from 0 to 65536. Numbers from 0 to 1024 are reserved for privileged services and designated as well-known ports. For example: 80 HTTP, 110 POP3, 443 HTTPS, 563 SNEWS, 569 MSN. Higher-level applications that use TCP/IP, such as Web Protocol and Hypertext Transfer Protocol, have ports with pre-assigned numbers.  Other application processes are given port numbers dynamically for each connection.

When a service (server program) is initially started, it is said to bind to its designated port number. As a client program wants to use that server, it must also must to bind to the designated port number. An example for the use of ports is an email client which you use to receive and send emails. Configuring email settings may be different from program to program, but all email programs require the same basic pieces of information. Among them are SMTP and POP3 email servers and their ports. The Simple Mail Transfer Protocol (SMTP) by default listens on TCP port 25 for incoming requests. The Post Office Protocol (POP) used to fetch email messages from the server listens on TCP port number 110. The following screenshot shows an account configuration window in a email application where you need to define POP3 and SMTP ports.

Incoming Ports and VPN Connection

Every VPN connection uses an incoming connection port on the user’s computer. It is like an endpoint to a connection. However, when connected to a VPN server, this server automatically becomes a firewall between you and the Internet. This can be very convenient because it gives you another layer of security and protection. Port scanning is usually associated with malicious cracking attempts. Closed ports prevent anyone from the Internet connecting to your computer. But remember,  connections with  legitimate purposes will be forbidden as well. To resolve this issue, Dynamic Remote Port Forwarding (DRPF) is used. TUVPN.COM has enabled DRPF for both PPTP VPN and OpenVPN service. Basically, this means that every time you connect to a VPN server, it gives you certain ports that will be automatically redirected to your computer. Any Internet connection to one of these server ports will be immediately directed to your computer through the VPN. Forwarding an individual port still requires you to change where your program connects, telling it to use a non-standard port rather than the standard port. Read more in FAQs (

Scanning Ports

If you are interested in ports issues, you can drill-down into the topic by using a free open source utility for network exploration Nmap ("Network Mapper"). Port scanning is the core function of Nmap. It was designed to rapidly scan large networks, but works fine against single hosts. Nmap runs on all major computer operating systems. The simple command

nmap <target>

scans 1,000 TCP ports on the host <target>. While many port scanners have traditionally ranged all ports into the open or closed status, Nmap range ports into six status: open, closed, filtered, unfiltered, open|filtered, or closed|filtered. The output from Nmap is a list of scanned targets, with supplemental information on each depending on the options used. A provided table lists the port number and protocol, service name, and state.


So, now you understand that incoming connection ports are the endpoint for communication via a network. The applications use the default ports until you configure the other ones. During VPN connection the default ports may need to be changed. TUVPN's personal VPN provides you a range of 5 ports to be used by your applications. With Business VPN services you can use as many ports as your working environment requires.


One Response to “Incoming Connection Ports (DRPF) Explained”

  1. Tweets that mention Blog TUVPN.COM - Incoming Connection Ports (DRPF) Explained -- Says:

    […] This post was mentioned on Twitter by TuVPN, tuvpnspanish. tuvpnspanish said: In this nice post we try to explain how Incoming Ports work (DRPF) and how they work along with you #vpn account […]

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