What is Port Forwarding |  use of ngrok |  Access localhost website from outside network

In computer networking, port forwarding or port mapping is an application of network address translation (NAT) that redirects a communication request from one address and port number combination to another while the packets are traversing a network gateway, such as a router or firewall. This technique is most commonly used to make services on a host residing on a protected or masqueraded (internal) network available to hosts on the opposite side of the gateway (external network), by remapping the destination IP address and port number of the communication to an internal host.



Port forwarding allows remote computers (for example, computers on the Internet) to connect to a specific computer or service within a private local-area network (LAN).[3]


In a typical residential network, nodes obtain Internet access through a DSL or cable modem connected to a router or network address translator (NAT/NAPT). Hosts on the private network are connected to an Ethernet switch or communicate via a wireless LAN. The NAT device's external interface is configured with a public IP address. The computers behind the router, on the other hand, are invisible to hosts on the Internet as they each communicate only with a private IP address. What is Port Forwarding ? use of ngrok ? Access localhost website from outside network


When configuring port forwarding, the network administrator sets aside one port number on the gateway for the exclusive use of communicating with a service in the private network, located on a specific host. External hosts must know this port number and the address of the gateway to communicate with the network-internal service. Often, the port numbers of well-known Internet services, such as port number 80 for web services (HTTP), are used in port forwarding, so that common Internet services may be implemented on hosts within private networks.





Typical applications include the following:

•     Running a public HTTP server within a private LAN
•     Permitting Secure Shell access to a host on the private LAN from the         Internet
•     Permitting FTP access to a host on a private LAN from the Internet
•     Running a publicly available game server within a private LAN

Administrators configure port forwarding in the gateway's operating system. In Linux kernels, this is achieved by packet filter rules in the iptables or netfilter kernel components. BSD and macOS operating systems prior to Yosemite (OS 10.10.X) implement it in the Ipfirewall (ipfw) module while macOS operating systems beginning with Yosemite implement it in the Packet Filter (pf) module.





When used on gateway devices, a port forward may be implemented with a single rule to translate the destination address and port. (On Linux kernels, this is DNAT rule). The source address and port are, in this case, left unchanged. When used on machines that are not the default gateway of the network, the source address must be changed to be the address of the translating machine, or packets will bypass the translator and the connection will fail.



When a port forward is implemented by a proxy process (such as on application layer firewalls, SOCKS based firewalls, or via TCP circuit proxies), then no packets are actually translated, only data is proxied. This usually results in the source address (and port number) being changed to that of the proxy machine.



Usually only one of the private hosts can use a specific forwarded port at one time, but configuration is sometimes possible to differentiate access by the originating host's source address.



Unix-like operating systems sometimes use port forwarding where port numbers smaller than 1024 can only be created by software running as the root user. Running with superuser privileges (in order to bind the port) may be a security risk to the host, therefore port forwarding is used to redirect a low-numbered port to another high-numbered port, so that application software may execute as a common operating system user with reduced privileges.


The Universal Plug and Play protocol (UPnP) provides a feature to automatically install instances of port forwarding in residential Internet gateways. UPnP defines the Internet Gateway Device Protocol (IGD) which is a network service by which an Internet gateway advertises its presence on a private network via the Simple Service Discovery Protocol (SSDP). An application that provides an Internet-based service may discover such gateways and use the UPnP IGD protocol to reserve a port number on the gateway and cause the gateway to forward packets to its listening socket.

Types of port forwarding

Port forwarding can be divided into the following specific types: local, remote, and dynamic port forwarding.

Local port forwarding

Local port forwarding is the most common type of port forwarding. It is used to let a user connect from the local computer to another server, i.e. forward data securely from another client application running on the same computer as a Secure Shell (SSH) client. By using local port forwarding, firewalls that block certain web pages are able to be bypassed.

Remote port forwarding

This form of port forwarding enables applications on the server side of a Secure Shell (SSH) connection to access services residing on the SSH's client side.[8] In addition to SSH, there are proprietary tunnelling schemes that utilize remote port forwarding for the same general purpose.[9] In other words, remote port forwarding lets users connect from the server side of a tunnel, SSH or another, to a remote network service located at the tunnel's client side.


To use remote port forwarding, the address of the destination server (on the tunnel's client side) and two port numbers must be known. The port numbers chosen depend on which application is to be used.


Remote port forwarding allows other computers to access applications hosted on remote servers. Two examples:


An employee of a company hosts an FTP server at their own home and wants to give access to the FTP service to employees using computers in the workplace. In order to do this, an employee can set up remote port forwarding through SSH on the company's internal computers by including their FTP server’s address and using the correct port numbers for FTP (standard FTP port is TCP/21).


Opening remote desktop sessions is a common use of remote port forwarding. Through SSH, this can be accomplished by opening the virtual network computing port (5900) and including the destination computer’s address.
   

Dynamic port forwarding

Dynamic port forwarding (DPF) is an on-demand method of traversing a firewall or NAT through the use of firewall pinholes. The goal is to enable clients to connect securely to a trusted server that acts as an intermediary for the purpose of sending/receiving data to one or many destination servers.[11]


DPF can be implemented by setting up a local application, such as SSH, as a SOCKS proxy server, which can be used to process data transmissions through the network or over the Internet. Programs, such as web browsers, must be configured individually to direct traffic through the proxy, which acts as a secure tunnel to another server. Once the proxy is no longer needed, the programs must be reconfigured to their original settings. Because of the manual requirements of DPF, it is not often used.



Once the connection is established, DPF can be used to provide additional security for a user connected to an untrusted network. Since data must pass through the secure tunnel to another server before being forwarded to its original destination, the user is protected from packet sniffing that may occur on the LAN.



DPF is a powerful tool with many uses; for example, a user connected to the Internet through a coffee shop, hotel, or otherwise minimally secure network may wish to use DPF as a way of protecting data. DPF can also be used to bypass firewalls that restrict access to outside websites, such as in corporate networks.

How to use Ngrok for Access outside Network ?

1) first we need a localhost server such as hosting provider or need a web address to access the outside network ( For eg Ngrok )


ngrok.com













Spend more time programming. One command for an instant, secure URL to your localhost server through any NAT or firewall.




2) Signup or login to ngrok and go to with download option for downloading a ngrok server ( application )


https://ngrok.com/download




3) First, download the ngrok client, a single binary with zero run-time dependencies. you can downloa for MAC OS X, Windows, Mac (32bit), Windows (32-bit), Linux (ARM), Linux (ARM64), Linux (32-bit), FreeBSD (64-Bit), FreeBSD (32-bit)...  


4)  On Linux or OSX you can unzip ngrok from a terminal with the following command. On Windows, just double click ngrok.zip.


  $ unzip /path/to/ngrok.zip 


Most people like to keep ngrok in their primary user folder or set an alias for easy command-line access.







5)  Try it out by running it from the command line:


  ./ngrok help 




6) To start a HTTP tunnel on port 80, run this next:


  ./ngrok http 80  











OR


  ngrok http -subdomain=baz 8080 


OR



  ngrok http foo.dev:80   




OR


  ngrok http https://localhost 


OR


  ngrok tcp 22 

How To Access website from Outside Network ?

Type the following command and press enter :-


1)   serivce apache2 start 


otherwise i have already download and install external apache server ( XAMPP Server )









For chech a service status , it's a start or not  


  service apache2 start 



then we have ready to access our localhost website via inside and outside network  ( internet )



Now, we have to copy a ngrok's link


https://ab5ac26e3592.ngrok.io








Then access






Through Mobile

Disclaimer

 

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You will not misuse the information to gain unauthorized access.
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