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Basically port forwarding allows computers over the internet to connect to specific computer or service within a private network. It basically makes your computer accessible over the internet even though you behind the router.
For example: friend of yours from their home wants to remotely connect your computer by using a service called Remote Desktop Connection (RDC)
RDC is a service built in Microsoft windows that enables you to connect to another computer running Microsoft windows. Once you connect in your remote computer you can use of it. If your friend is ready to connect your computer so we have to start of RDC and send request your public IP address with specific port number now port is in physical connection but its logical connection that is used by programs and services to exchange information. Ports legally identify the programs and services that are running on a computer. And this case RDC uses port 3389 so request with the port number make it way to internet to your router. Once it reaches to your router your router needs to know where to forward the request for port 3389 because without any port forwarding configured, your router does not know what to do with this request. This known port forwarding covers in.
We are going to tell our router to send or forward any request that come with router 3389 and send the request to our computer. So do this we need to log into routers configuration page by typing in the routers internal IP addressing using a web browser.
If enter a routers private IP address you just open command prompt in windows computer and type ID configuration and press enter. The default gateway is the internal IP address of your router. And also important to know computer IP address in which is right IPv4 address, because we are going to enter this address in the port forwarding configuration page.
In web browser we enter the IP address of the router and we are now in router configuration page depending upon want router you are using configuration page will be different. Depending upon which brand you are using. Here it is used LINKSYS by Cisco.
Whatever type of router we are using the layout will be different basically you need to go to port forwarding section to configure port forwarding.
In port forwarding page enter the name of application called as remote desktop connection and we have forward RDC port to the computer. Enter port umber which happens to be 3889. Then you have to pointed IP address of the computer your friend want to access. 192.168.1.2 And save a setting and done. Now your friend sends request sends port 3389 router knows where to forward that request to and now the connection is completed.
If we still confused about ports lets illustrate what is port and how it works.
Here it is having a phone with electronic switch board typically being used by a company. If same one wants to call this company and wants to talk to sales department within this company. Dial with phone number with extension of the sales department. When the call comes in the phone will answer the call and phone will look at the extension number and send or forward the call to corresponding department number. So let’s say the other person calls company and they want to speak to support department so then call comes is and receive by the phone, phone has done its job. Which sends call to specific company from the outside bit once the call is received using the phone number, the phone number ni longer needed because it done its job. Only thing it needed now is the extension now phone will forward the call to support department because of extension number.
This works similar to network. In network router is contact with IP address along with a port number. The router will look port number send or forward its request to the internal IP address that port has been configured. The other request from the internet comes into network and reaches the router the IP address done its job which brings the request to router from the internet. IP address is no longer needed because it’s already done its job. Now router will look port number and based on port forwarding configuration now forward the request computer with the IP address port has been configured.
In a network IP address is similar to phone number and port number is similar to extension. The router represents the phone and computer with network represents different department.
Ports are always associated with an IP address and are identity by the unique number. Port number if we see or not the port number is always associated with IP address because IP address always has a purpose and it uses port number determine. What the purpose whether it pulling up a web page using FTP service or using RD. The IP address always determined by the port number but port number not only associated with IP address but it always associated with application or process. Such as FTP, web page and email so on.
The port number range is 0-65535, out of 65535 the few of these are common and are used daily basis such as
Port 80 – HTTP- used for web pages
Port 20 & 21- FTP- used for file transfer protocol
Port 443 –HTTPs- used to bring secure web pages.
These are just few ports. The privilege category of ports called well known ports which ranges from port 0 – 1023.