Hi I am new to socket programming.I am developing a client- server application. My server will a Java application. My client will be an android App. what i want to do is that i want to send data over both the channels i.e WiFi and 3G network. Is this Possible to send some packets over WiFi and some over 3G.
Is such a mechanism possible. If yes how can i accomplish this?
what I thought that i will create two sockets at client side and bind them to their specific IP's i.e bind one socket with wifi IP and other with 3G network IP.
Is there any provision of binding IP's with sockets at client side.
Related
I am busy with a project where I'm creating a basic client/server chat application which allows a user to create a server on their local network on a port of their choice and then have multiple clients connect to that server by specifying the IP and port number of the server(So far so good).
I would like to how I can have clients see all the possible servers they can connect to on their local network when there are multiple servers running on their local network over different ports and then allowing them to connect to one. I am using basic Java socket programming for this project.
You could have
use a UDP based protocol where each server publishes it's IP:port every second.
you could have a service where each server registers. You could chat with that to get the list of all services.
The nice approach of the later option is you can use one of your chat services for server discovery. When you want to get the list, you send a message to a channel on that server which all the servers are listening to and they respond with a chat message.
i am using this tutorial as guide. i am creating an android app which is basically chat application. this uses socket programming to communicate .
i want to connect directly to device and deliver the message. the message does not go to server. server only tell me the address of the device thats it.
i followed the tutorial i mentioned above and this only works for the case where client and server are within same wifi/network. i want to connect to server from client irrespective of their network connection place. how do i do it from any network to any network.
i think i need to use port forwarding , but this is not practical . so we better use a server for keeping track of all the ip changes. and deliver the messages directly from the source to client. so how do i do it. please suggest any resources.
update
as of now what i studied is i have to use innetaddress to communicate if i am inside an wifi router.
thank you
I have developed a TCP server with Android SDK code using the ServerSocket class.
I want this server to work only on the cellular network (3G/4G) and not on the wifi network. To be more precise I want it to listen only connections from rmnet0 interface, not from the wlan0 one.
Any idea?
I want to
Recieve UDP message on device when it is connected through wi-fi
Know how to send udp message on device when it is connected to wi-fi
router as the sender on diffrent network
What i have tried
http://code.google.com/p/boxeeremote/wiki/AndroidUDP
What is working
UDP messeges are being recieved on device when it is connected
through 2g/3g data service
UDP messeges are being recieved when sender and reciever are both in
same network ( behind wi-fi router )
Any help/point in right direction is appreciated.
When the device is behind a wi-fi router, it has a private address so it isn't reachable from outside the private network, at least no without some extra work.
You need to do Hole Punching, is what applications like Skype do to receive UDP packets. Applications usually use a STUN server in order to achieve this.
The easiest alternative would be to have a server with a public address and make all the devices connect to the server with tcp/ip protocol. If you can't afford that you need to do Hole Punching.
I am trying to create a java chat application for my networking class. As of right now I am stuck trying to connect to someone behind a different router. The way I have my project right now is I have a client program and a server program. The client programs first logs into the server program which logs their IP and port in a database and then the server gives them back the list of their friends with their IPs and ports. Then the client closes down the connection to the server and tries to connect to another client using the information the server sent back. So far my program only works connecting to the server and getting the friends IP and port but when I use those values to connect to the other client I cant connect.
socket = new Socket();
socket.setReuseAddress(true);
socket.setKeepAlive(true);
socket.setSoLinger(true, 10);
socket.bind(new InetSocketAddress(Port));
socket.connect(new InetSocketAddress(host, SERVER_PORT));
reusePort = socket.getLocalPort();
Above is a snippet of java code used to connect to the server then below is what i do on the client side.
ss = new ServerSocket(reusePort);
So now technically I am listening on the same port I used to connect to the server with which is logged in and is retrievable to another client and is in the NAT table with my ip and port. I am not sure what I am missing or if there is some protocol or something that I have to do. I have looked at TCP and UDP hole punching but I am not sure how that is actually accomplished or how to implement it.
Any suggestions would be appreciated.
If you want to send a message you'll need to set up port forwarding on any device that acts as a server (any device which creates a socket server). Port forwarding is done on the Router. The reason you cannot connect to the other client is because they are hidden behind their routers firewall. Their address to the rest of the world is actually the address of the router, not of their physical computer. On their local network they have a different address then what the rest of the world sees, and the router figures out what messages from the outside world need to be sent to the client based on an address translation table.
Given your architecture, this would mean that all clients need to have their routers doing port forwarding, which is of course unfeasible (imagine gtalk or aim requiring users to do port forwarding).
The more common architecture is to have the Server do the work of rebroadcasting messages to the connected clients and maintain tables to lookup whose talking with who. This way there is a single server which will need a static ip (or be port forwarded), and all users are simply clients which connect to the server socket and read messages from it.
For actual code describing the second architecture please see http://pirate.shu.edu/~wachsmut/Teaching/CSAS2214/Virtual/Lectures/chat-client-server.html. Then the machine which is running the server code either needs a static ip or if it is behind a router needs traffic from the port it is listening on to be forwarded.
So on the server code you will bind to the ip assigned from your router (something like 192.168.1.2 at some port say 5000). Then go to your routers configuration page (it may be 192.168.1.1 see http://www.wikihow.com/Port-Forward/Open-Ports-on-a-Linksys-Router), and forward port 5000 to the address 192.168.1.2.
The Interactive Connectivity Establishment (ICE) protocol combines various NAT traversal utilities such as the STUN and TURN protocols in order to offer a powerful mechanism that allows Offer/Answer based protocols such as SIP and XMPP to traverse NATs.
This project provides a Java implementation of the ICE protocol that would be usable by both SIP and XMPP applications. The project also provides features such as socket sharing and support for Pseudo TCP.
ice4j is maintained by the Jitsi community.
ice4j