I am trying to develop a lan chat application. As I looked for the topic, I found that whatsapp, viber etc. use a server which controls all the traffic. The server tells the status of devices and manage all traffic etc. So, what am I trying to know is :
How the server gets the info of devices like, IP address, MAC address etc?
How the data is transferred from one client to server and then server to another client?
Which language should I use server side?
As shown in image, I want to connect two devices, A and B and interchange data between them.
Actually, I'm not sure data always through the server. From what I know, the client logs in at the server the first time it connects only. If client A wants to send a message to client B, it retrieves the IP corresponding to username_B from the server, then exchange of data is done directly between client.
What you should do is to develop a protocol to login at the server and register the client IP, and to retrieve an IP from a username.
For the routers between server and clients, I think it is out the server scope, you just need for NAT.
Related
So I am trying to create a p2p file sharing application in Golang. I am running a globally accessible server for the purpose of sharing IP addresses of 2 clients. When both the clients have each other's IP addresses, they can use hole punching to share the files.
But I am facing some problems in the hole punching part. When I send a request to server, the server is going to store the address of the client and it will later relay this address to other client. Problem is that the address being stored on the server is different than the address that is being is used for Hole punching. Suppose that address being stored on server is NATrouterIP1:PORT-A for first client and NATrouterIP2:PORT-B for the second. But when I am using the first client to send a message to second client, it shows that the message was sent from NATRouterIP1:PORT-C. PORT-A generally stays around 65000. But this PORT-C is 1024. For my application to work these ports should be same. Can someone explain what the issue is?
Github: https://github.com/killtheverse/go-send
[This post has been updated with a possible approach, which is added to the bottom]
I am trying to create a web socket connection between two devices((A). chrome in different computer and (B) a raspberry pi) in different networks. Thus, i can send video data over websockets. However, I cannot port forward the network of my router to expose my local IP to the network, thus, I can't send the data right away.
Figure below explains the architechture.
Thus ,I am trying to implement a logic so that Device A websockets the public ws of the cloud while, the cloud actually gets the data from Device B.So Device A websockets device B indirectly.
Device A<==>Cloud Server<==>Device B
The cloud could be something like a proxy or a relay websocket server.
The video feed needs to be sent in real time,
Please suggest how can i proceed with it.
Additional note, i have acquired an instance of digitalocean as VPS, following the blog Accessing home services from anywhere, without port forwarding! but not sure how to proceed.
Update(11th Nov,2019):
I am planning to use a websocket server on DigitalOcean instance(droplet),which would be listening to my local IP/port of my raspberry pi.And this VPS would act as a websocket server,which would redirect the traffic.
However, I am unsure how to use the same.And need your kind suggestions.
I know already about the web-sockets, and they are great, the problem with them is that they have to keep the connection open in order to be able to communicate.
I have a small system where from time to time the server has to update the status and notify the clients about that, and keeping the connection open from every client is not so optimal. At same time is very important that the update on the client side to be made just in time.
So my question is, if the server has a unique address does the client have a public temporary address where the server can send request? So when the client will connect to the server it will provide it's unique address and the server will cache it, and when there will be an update the server will send the request to that address?
I understand that there many problems as the address will constantly change, but this is already other question.
If client does not have a dedicated IP-address then it is not available from WAN unless it has an open connection with any node in it.
When client from local network sends request to a server it's (client's) router remembers client's local IP-address and port and translates it using NAT protocol to one of router's free ports and then sends data further with router's own 'IP-address of the sender' in IP protocol header and 'Sender's port' in TCP header. When router get's server's response it uses NAT table from it's memory to translate addresses back and deliver data to the client. Addresses are normally kept in NAT table while connection between server and client is open. So if there are no opened connections between server and local network client then server will not be able to connect with client because server does not know how to reach it.
You say you have a small system. Why then do you think that you will not have enough free ports at your server to work with websockets? If you just want to get updates from the server (not to both send and get data through a persistently opened connection) you'll probably find long polling or SSE more suitable. It is definitely easier to implement than websockets.
I am working on a small project to help me understand websockets better. I am making a simple browser game that connects to an ip via a websocket. There will be 3 ip addresses however I want to assign the user an ip and not have them able to modify it so they are unable to get on the same server as friends.
I will assign the ip based on how full the games are etc and this will be down via php. Currently although it connects to this ip, the user is able to use the console in a browser to modify the ip to one of the other ones.
I was thinking of sending a check number, so the web server sends this to the user along with the ip. It also sends it to the websocket server. Then when a user connects if the check number doesn't match it rejects the connection.
I'm new to websockets so I'm not sure if this would be easy to implement, so are there any easy solutions to this?
That seems to be the duty of other element, in particular the load balancer. How are you balancing the requests across those 3 servers? Does your load balancer support sticky sessions?
If not, probably you can record to which IP address the user connected first, and they if it connects to one of the other two later, you can return a HTTP 302 (Redirect) pointing to the server you want.
Cheers.
I am new to Websockets. While reading about websockets, I am not been able to find answers to some of my doubts. I would like if someone clarifies it.
Does websocket only broadcasts the data to all clients connected instead of sending to a particular client? Whatever example (mainly chat apps) I tried they sends data to all the clients. Is it possible to alter this?
How it works on clients located on NAT (behind router).
Since client server connection will always remain open, how will it affect server performance for large number of connections?
Since I want all my clients to get real time updates, it is required to connect all my clients to server, so how should I handele the client connection limit?
NOTE:- My client is not a Web browser but a desktop application.
No, websocket is not only for broadcasting. You send messages to specific clients, when you broadcast you just send the same message to all connected clients, but you can send different messages to different clients, for example a game session.
The clients connect to the server and initialise the connections, so NAT is not a problem.
It's good to use a scalable server, e.g. an event driven server (e.g. Node.js) that doesn't use a seperate thread for each connection, or an erlang server with lightweight processes (a good choice for a game server).
This should not be a problem if you use a good server OS (e.g. Linux), but may be a limitation if your server uses a desktop version of Windows (e.g. may be limited to 200 connections).