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?
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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.
I have a question about network connections among computers.
I've made some applications where messages pass through the Internet (via sockets) to make a connection between two devices. However, a strong condition is that two devices must be connected to the same network.
Can anyone give me a trick how to create a communication using sockets between two computers even if they are connected to different netwkorks?
Thank you in advance.
Here is a great tutorial on how to use sockets and general networking
(in java) http://www.thenewboston.org/watch.php?cat=25&number=38
In order to communicate between two diffrent networks over the internet, you will need to do something called port forwarding. What that does is that when your public IP of your network receives a packet with a spesific port number. The router knows where to send that packet to which local IP.
If you dont port forward and receive some data. The router doesent know where to send the packet. Therefore it discards it, which means others wont be able to connect to you.
You will only need to port forward the network with your server (using the example i linked). How you do that is by logging in to your router, and say that a port which the server uses gets forwarded to the IP of the PC hosting the server.
On the other network (client) you will need to change the IP address of which the client shall connect to. That IP address needs to be your public IP of your server's network. You can find that by connecting to the server's network and go to: http://www.whatsmyip.org/ . Keep in mind that public IP addresses may change over time.
Hope this helped!
-Kad
I want to connect my PC-with-arduino (server client) with TCP/IP socket. In my PC i have written java code to make this happen. My questions are : I have to make port forwarding to my router? If yes, i will pass the port socket(client-server) into router? I have the zte zxv10 h108l router and i can't find any instructions about port forwarding for this model!
You say locally, which means you do not need any port forwarding. All your devices are on the same subnet, and you can directly open connections with each other.
Port forwarding would only be necessary if something outside you network wants to open a connection to something inside. Basically, if something on the WAN side of the router wants to open a connection to something on the LAN side. For example, you at a coffee shop on your laptop connecting to Arduino in your house.
Note that the reverse does not hold: something on the LAN side can open a connection to something on the WAN side with no port forwarding -- that is the NAT function of the router and is always active. For example, that is how your computer connects to stackoverflow with no special configuration on the router.
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.