I have 'Socket test v-3.0' software installed on two different PCs.
Using it can create a TCP server on 1st PC and a TCP client on 2nd PC.
When I connect both the PCs on LAN I can establish a connection & can communicate between the Server & Client.
But, When I connect both the PCs to individual Internet connections (Using dongles having different ISPs), I couldn't establish the connection between the Server & Client.
How can I do that?
Please help me out..
The private address 192.168.x.x is address that can be used for direct connection only in your private network. If you want to connect to your machine from public internet you have two options:
Get a public IP address
Configure a port forwarding
Public IP address could be get from your internet provider but it is usually requires some extra payment dependent on your service provider policy.
Port forwarding can be configured at the device at the border between your private network and internet. The device does the NAT (network address translation) between your private network and intenet. Use google if you are not sure about NAT.
Such a device can be your own device like an ADSL modem or a set top box. But such a device could be in the internet provider network. If you own the device then you can configure the port forwarding yourself. Modems usually have a web interface where you can easily configure port forwarding. See the documentation to your modem or whatever you have.
If the NAT device is in internet provider network then you have to ask it to configure port forwarding for you. Before you ask please read something about port forwarding so you are sure what you want to configure.
Related
For two device both has public IP address, we can use socket IP and port to setup socket communication.
If both device do not has public IP but connect to sub-Lan then access public network through router (no port mapping in router), how can this two device setup socket connection?
For example in above diagram, how can machine A communicate with machine C?
Assuming that you have not set up a VPN tunnel between the two routers that connects both branches of the 192.168.1.0/24 network then the answer is: you can't.
If you set up a VPN tunnel then each side of the 192.168.1.0/24 network will be able to see the other side. Please note that the routers will need to be able to do ARP spoofing, i.e. the router for A & B will need to be able to spoof the MAC for C, i.e. intercept IP packages for C on their LAN and forward them through to the VPN to the other network half where they are delivered to C.
If you set up at least one port forwarding on one router, then you'll have other options, e.g. an SSH tunnel on C that connects to the port forward on either A & B. You can then use the -L option on C to setup port forwarding through the SSH tunnel to the other half of the network.
When we ping to any Public IP of a router it give a reply,
we dont get reply, if we ping a local computer with its private IP of a particular network,
So is there a way so I can make direct connection or socket with a particular PC in a network.
I have heard that, I have to make connection with public IP of a particular network and the port number will decide, on which PC in that network , my request will go.
But this method is not working..
If the computer is behind a router that uses Network Address Translation (NAT) - that is, the computer has a private IP that is not visible to the internet - then you cannot ping or establish a connection to the computer from the outside. This is because the router does not know which computer you want since all the computers behind the router share the same public IP address.
The way to establish a connection in this case is to have the computer which is behind the router establish the connection to the outside computer. For example, when you go to a web site, you can do it from a computer behind a router since your computer is initiating the connection. However, the web server you are going to must have a public IP.
When a computer behind the router initiates a connection, the router does select a port number to associate with that connection so packets from the outside for that connection will go to the right computer. However, this only works for traffic on that particular connection; the port number is not a general purpose mapping to that computer.
Two computers behind the same router can establish connections with each other using the private IPs as they don't have to go through the router to do it.
You can decide with your friend who is going to be the client (the one initiation the TCP connection) and who is the server (the one receiving the TCP connection) and which port should be used (let's say X). Let's say that your friend is the server. Then he/she has to configure his/her router to redirect all the traffic to the router to port X to his/her private IP to port X (this is what Warren mentioned as NAT).
If you use a port above 1024, the server (running on your friend's PC) doesn't need root/administrator privileges.
Your program (the client) would then connect to the public IP address of your friend. He/she can check his/her public IP with: What is my IP
I like to connect to a TCP server that run in a machine that is connected to the LAN in my home network. This LAN can be connected to internet via either following methods.
1. Through a router which has a wireless or wired WAN connection
2. Through a router which uses a mobile broadband connection, for example a router that accept a USB modem to connect to internet.
I know in the first case, we can use port forwarding.
In the second case, I believe telcos use PPP protocol and port forwarding does not work.
In addition, even in the first case, if ISP does not give a static IP, then we need to use DNS mapping service to map a fixed URL to the allocated dynamic IP and we need to configure router to go and register the dynamic ip at the start up.
My question is, are there any other better methods that can be used in this situation? I am wondering how chat applications connect to each other? I hope they maintain a TCP connection between two devices, without a central relay server?
I'm writing a C# remote control for my media player. It runs on my Android phone.
I have a client app listening for TCP connections on my computer which, one a connection has been established, processes commands (Volume up, volume down, ...). I've tested that part using telnet 127.0.0.1 on my computer, and it works great.
Things are trickier when it comes to connecting from my phone, since it's not on the same network (I don't have Wi-Fi, only wired connections), so I'm not sure how to proceed. Basically I want to connect to a computer that's behind a router.
Should I rather host the TCP server on my phone, and have the PC connect to it? Take IRC as an example: although I'm behind a router, I can connect to servers outside, without port forwarding.
Or if hosting the server on my computer is fine, how do I connect to it?
I don't understand everything to this yet, so feel free to correct me if I got something wrong.
It would be more logical to keep the PC hosting the server, and configure your router to forward connections to your PC. You have two options:
Establish a DMZ: all incoming connections on the router will be forwarded to one PC only. This is easiest when you only have 1 PC on the network that needs to accept connections.
Configure port forwarding: you can instruct the router to forward connections incoming on port X to the IP Y on port Z. This way, multiple PC's can listing for connections (using different ports on the router). It is also a bit more secure.
How to set these up depends on your router, but most routers just accept connections on their port 80 and offer an easy web-interface. If you give your router brand, we can link you to the manual.
Things are trickier when it comes to connecting from my phone, since
it's not on the same network (I don't have Wi-Fi, only wired
connections), so I'm not sure how to proceed. Basically I want to
connect to a computer that's behind a router.
What you want to achieve is possible, but you need to learn about NAT traversal and hole punching.
Most often, devices behind a NAT/Router have a private IP address only valid on the LAN. Remote devices can't guess it. This private address is translated into a public IP address by the NAT when the device wants to communicate with the WAN.
The easy solution is you can give a public IP address to the device behind the NAT. In this case, remote devices on the WAN will easily be able to reach it, because its address is public.
I want to connect to a system which is behind a router. I know the public address of the router as well as the private ip (fixed always) of the system. How do i establish socket connection with the private ip?
This is why some people say that they are behind a "firewall", when they are behind a router. The Evil Viruses Of The Internet are not able to exploit any software on a computer behind a router (provided that the router admin didn't configure it in the funny way, for example by enabling DMZ).
You still have some options:
Talk to the router admin and make him forward a port for You
Take the router out and put Your "target" computer where Your router was, or enable DMZ (this only makes sense if there was only one computer behind the router). Warrning: install a firewall on the target computer first!
Turn the socket 180 degrees. Make the computer behind a router establish the connection to the server that has a public IP address
Use something like UPnP, if Your router supports it
Get a dedicated IP address for Your computer and configure router to switch all traffic to this IP address to Your computer (this is similar to DMZ, but would work if You have more than one computer behind the router). Warrning: install a firewall on the target computer first!
Use NAT traversal. There is a very good article on the subject here. Simplified version is that client establishes connection to some remote server. The server can see the opened port number on the client's router and this port is assigned to the client's machine, so it (or some another computer sharing this information) may establish connection to that port and reach the client's application. Warrning: this doesn't work with all routers. Some routers just won't let this happen.
The simplest thing is probably to forward the port from the system you want to connect to through the router.
This is more a question of configuration of the router as opposed to your actual program. If the router isn't configured to forward traffic to the private system, there's no way to force it to connect you - rather, the private system would have to open the connection on its own.
Strictly speaking, the answer to your question is "you can't". You can however enable DNAT (Destination Network Address Translation) on your router. You connect to a certain port on the router, and it forwards the connection to the internal ip. The internal ip (and port) are configured in the router settings and are not known by the connecting client.