I'm having 2 apps that communicate via unix domain socket on linux.
After running the apps, I see a file corresponding to the socket path name was created in file system.
Then I tried with a scenario as below:
Start server app, server is listening now
Delete the file that created by above server from terminal
Start the client app.
The result was: server still listens forever, and client failed to connect to server.
My question: Is there any way to protect the socket file from being removed while it is in used (e.g: hide it completely from other processes, or lock it until the owner release the lock)?
Related
I having some doubts that:-
what is need to use the socket.io client we can use only the socket.io server to stop refreshing the app.
what is different between the socket.io client and socket.io server.
check this link
socket-io.client is the code for the client-side implementation of socket.io. That code may be used either by a browser client or by a server process that is initiating a socket.io connection to some other server (thus playing the client-side role in a socket.io connection).
A server that is not initiating socket.io connections to other servers would not use this code. This has been made a little more confusing that it probably should be because when using socket.io, it appears that both client and server are using the same socket.io.js file (because they both refer to a file with the same name), but is not actually the case. The server is using a different file than the client.
From the Github page for socket-io.client:
A standalone build of socket.io-client is exposed automatically by the socket.io server as /socket.io/socket.io.js. Alternatively you can serve the file socket.io.js found at the root of this repository.
Keep in mind that there are unique features that belong to client and server so it should not be a surprise that they use some different code. Though they share code for parsing the protocol and things like that, the server has the ability to run a server or hook into an existing web server and it has methods like .join() and .leave() and data structures that keep track of all the connected sockets and is expected to live in the node.js environment. The client has the ability to initiate a connection (send the right http request), do polling if webSockets are not supported, build on a native webSocket implementation if present, etc....
I'm trying to develop a web application in nodejs. I'm using an npm package called "simple-peer" but i don't think this issue is related to that. I was able to use this package and get it working when integrating it with a laravel application using an apache server as the back end. I could access the host machine through it's IP:PORT on the network and connect a separate client to the host successfully with a peer-to-peer connection. However, I'm now trying to develop this specifically in node without an apache back end. I have my express server up and running on port 3000, I can access the index page from a remote client on the same network through IP:3000. But when I try to connect through webrtc, I get a "Connection failed" error. If I connect two different browser instances on the same localhost device, the connection succeeds.
For reference: i'm just using the copy/pasted code from this usage demo. I have the "simplepeer.min.js" included and referenced in the correct directory.
So my main questions are: is there a setting or some webRTC protocol that could be blocking the remote clients from connecting? What would I need to change to meet this requirement? Why would it work in a laravel/webpack app with apache and not with express?
If your remote clients can not get icecandidates, you need TURN server.
When WebRTC Peer behind NAT, firewall or using Cellular Network(like smartphone), P2P Connection will fail.
At that time, for fallback, TURN server will work as a relay server.
I recommend coTURN.
Here is an simple implementation of simple-peer with nodejs backend for multi-user video/audio chat. You can find the client code in /public/js/main.js. Github Project and the Demo.
And just like #JinhoJang said. You do need a turn server to pass the information. Here is a list of public stun/turn servers.
I came across this awesome library xterm.js which is also the base for Visual Studio Code's terminal. I have a very general question.
I want to access a machine(ssh into a machine ) on a local network through a web based terminal(which is out of network, may be on a aws server). I was able to do this in a local network successfully but I could not reach to a conclusion to do it from Internet-->local network .
As an example - An aws server running the application on ip 54.123.11.98 which has a GUI with a button to open terminal. I want to open terminal of a local machine which is in a local network somewhere behind some public ip on local ip 192.168.1.7.
Can the above example be achieved using some sort of solutions where i can use xterm.js so that I don't have to go for building a web based terminal? What are the major security concerns I should keep in mind while exposing the terminals this way ?
I was thinking in line with using a fixed intermediate server between AWS and local network ip and use some sort of reverse ssh tunnel process to do this but I am not sure if this is the right way or could there be a more simple/better way to achieve this.
I know digital ocean, google cloud , they all do this but they have to connect to a computer which has public ip while I have a machine in a local network. I don't really want to configure router to do any kind of setup .
After a bit of research here is working code.
Libraries:
1) https://socket.io/
This library is used for transmit package from client to server.
2) https://github.com/staltz/xstream
This library is used for terminal view.
3) https://github.com/mscdex/ssh2
This is the main library which is used for establishing a connection with your remote server.
Step 1: Install Library 3 into your project folder
Step 2: Start from node side create a server.js file for open socket
Step 3:
Connection client socket to node server (both are in local machine)
The tricky logic is how to use socket and ssh2.
On emission of socket you need to trigger an SSH command using the ssh2 library. On response of the ssh2 library (from server) you need to transmit the socket package to the client. That's it.
Click here to find an example.
That example will have these files & folders:
Type Name
------------
FILE server.js
FILE package.json
FOLDER src
FOLDER xtream
First you need to configure your server IP, user and password or cert file on server.js and just run node server.js.
P.S.: Don't forget to run npm install
Let me know if you have any questions!
After some research later I came across this service : https://tmate.io/ which does the job perfectly. Though if you need a web-based terminal of tmate you have to use their ssh servers as a reverse proxy which ideally I was not comfortable with. However, they provide tmate-server which can be used to host your own reverse proxy server but lacks web UI. But to build a system where you have to access a client behind NAT over ssh on web, below are the steps.
Install and configure tmate-server on some cloud machine.
Install tmate on the client side and configure to connect to a cloud machine.
Create a nodejs application using xterm.js(easy because of WebSocket based communication) which connects to your tmate-server and pass commands to the respective client. (Beware of security issues of exposing this application, since you will be passing Linux commands ).
Depending on your use case you might need a small wrapper around tmate client on client-side to start/stop it automatically or via some UI/manual action.
Note: I wrote a small wrapper on client-side as well to start/stop and pass on the required information to an API server (written in nodejs) which then pass on the information to another API which connects the browser to the respective client session. Since we had written this application it included authentication as well as command restrictions of what can be run on terminal. You can customize it a lot.
I'm building a desktop application where clients will interface with the server through the browser, but will also connect to eachother using a local node.js server. This means that every client has a local node.js server running.
I want to allow users to connect to the central webserver with the browser, and then initialize direct connections to other client's local node.js server. Is there a production ready way to expose a local node.js server to the outside world, or otherwise proxy the connection between the two?
Right now, my solution is to use localtunnel to expose the server, and then make a connection. As far as I understand, this is not recommended, and I'm looking for something better.
Okay, so I have created an ubuntu vm in the azure cloud, I have successfully launched nodejs, redis, socket.io, Express and all the components for a game I am writing.
I have setup azure endpoints on internal and external port 8080, and use app.listen(8080) in my js code.
When I browser to http://< app-name >.cloudapp.net:8080/ I can view the result of my nodejs application fine, it displays the html, css etc.
However when it attempts to start a socket connection (using socket.io) I get only this (on my chrome dev console under websockets):
HeadersPreviewResponseWebSocket Frames
Request URL:ws://<app-name>.cloudapp.net:8080/socket.io/1/websocket/13510496541533398587
Request Method:GET
Status Code:101 Switching Protocols
Request Headersview source
Connection:Upgrade
Host:<app-name>.cloudapp.net:8080
Origin:http://<app-name>.cloudapp.net:8080
Sec-WebSocket-Extensions:x-webkit-deflate-frame
Sec-WebSocket-Key:y5vueHE66phl70gle7KCtw==
Sec-WebSocket-Version:13
Upgrade:websocket
(Key3):00:00:00:00:00:00:00:00
Response Headersview source
Connection:Upgrade
Sec-WebSocket-Accept:dn+2lA6sMIXHLEmDS/Q4j/IIwxI=
Upgrade:websocket
(Challenge Response):00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00
It will also crash the nodejs app on azure when i try send anything using socket.emit() on the client (browser); in my azure ssh, it just says 'DEBUG: Program node app.js exited with code null' which isn't particularly helpful.
So it obviously isn't connecting properly? I have also tried in my nodejs listening on port 80, but then I don't even get the standard webpage (html,css,etc).
From what I have read online, it is very possible to get sockets working providing your not using the web role (which I assume the vm is not).
Any idea how I can get this to work? (and preferably on port 80)?
Edit: starting to wonder if this has nothing todo with sockets, realized I get the same switching protocol message, on my home vm (where it is working). Spin off question: How can I view crash details for a nodejs program on a ubunu azure vm?
There is a time out of around 60s on the Windows Azure loadbalancer.
Does it work if you send a message back to the client just after the websocket connection is established?
If it is the case you will have to implement some keep a live message send every minutes.