using w10/64, python 3.6, rpyc
I have a server receiving serial data and want the data to be published to any client asking for a connection.
In the server I add every client into a connection list and when detecting changes in the data publish it to all clients.
Clients send a "startListening" request to the server including ip and port. The server then opens its own connection to the client to update it with the new data.
I have an "on_disconnect" method in my servers commands class and it gets triggered when a client stops.
When the client restarts and sends a "startListening" again I get an EOFError on the server showing the clients ip/port.
How can I properly detect and close the client connection to allow for a reconnect?
Related
I'm new in socket-io. socket-io working fine but keep sending connect request infinitely to server.
Here is my client ts :
private url = environment.socketServer;
constructor() { this.socket = io(this.url) }
The usual reason for a socket.io client to try to connect over and over is if the socket.io version on the server and client are not compatible. The client connects, the server finds the version is incompatible and drops the connection and the client then tries to connect again, over and over.
Other possible issues:
Server infrastructure (such as load balancers, proxies, firewalls, etc...) are not properly configured to allow webSocket connections.
You're trying to connect to a cluster, but it isn't configured for sticky connections that will "bind" a socket.io client to the same server.
You're confused about how a socket.io connection starts. It is normal for the client to start with a couple web connections in a row (polling) until it realizes that both sides support a webSocket and then socket.io switches over to webSocket.
I am using a websocket library on server for establishing socket connection.
https://github.com/websockets/ws
I have a more than one server in cluster, I want to know how can I use same socket connection object on another server in cluster.
And also I want to know what is the best option for webchat implementation native websocket or socket.io
You cannot use the same actual socket object across multiple servers. The socket object represents a socket connection between a client and one physical server process. It is possible to build a virtual socket object that would know what server its connection is on, send that server a message to then send out over the actual socket from that other server.
The socket.io/redis adapter is one such virtual ways of doing this. You set up a node.js cluster and you use the redis adapter with socket.io. It uses a central redis-based store to keep track of which serve process each physical connection is one. Then, when you want to send a message to a particular client from any of the server processes, you send that message through socket.io and it looks up for you in the redis database where that socket is connected, contacts that actual server and asks it to send the message to that particular client over the socket.io connection that is currently present on that other server process. Similarly, you can broadcast to groups of sockets and it will do all the work under the covers of making sure the message gets to the clients no matter which actual server they are connected to.
You could surely build something similar yourself for plain webSocket connections and others have built pieces of it. I'm not familiar enough with what exists out there in the wild to offer any recommendations for a plain webSocket. There plenty of articles on scaling webSocket servers horizontally which you can find with Google and read to get started if you want to do it with a plain webSocket.
I am developing a WebSocket service using NodeJS and Einaros WS module and I have raised this question: NodeJS Einaros WS Connection Timeout which apparently no one know the answer so I presume I should write my own ping pong based system to check whether a client is still connected or not.
I am not sure whether I should write code on server side or client side; I mean if the server should ping the client or... the client (which is my own websocket application) should ping the server.
Is there any difference between both methods ?
It is called a heartbeat and is usually sent by the client every 5 seconds with a ping frame (0x09) as opcode while the server responds with a pong frame (0xA) as opcode.
In theory it doesn't really matter whether it's the server or client initiating the heartbeat, but in a real-world situation it is usually better that the client keep itself updated whether the server is there or not to be able to inform the user as quickly as possible.
Suppose you connected to a server through socket connection and for onetime you send the request to the server and receive the response then again you try to send the request to the server but send(); returns -1 because server was down after a while server comes up,can you use the same socket to send request to the server ?
No, when you get the error the connection is no longer valid. Once a connection is invalidated, you should just close the socket; you can't reuse it for a new connection. If the server has gone down, it has no memory of the parameters of the original connection (e.g. port numbers); you need to open a new connection so that the client and server will be in sync.
if the server is connected to a websocket client using socket.io, what are the events that would cause the client.id to change?
the server reset
the client opening a new connection
are there others, such as timeout?
When client connects to the socket.io server, then new id is generated for the connection. And there is no other place where id is generated.
Server reset, client opening new connection, timeout (and reconnection) - all of these trigger creation of new id, because actually client has to create a new connection to the socket.io server.