Keep client connected to WebSocket in react native and express server - react-native

Question

I have a react native application where i have two users using the app (customer and restaurant)
So on checkout I connect the customer to websocket on the express server and once the order is placed i send a message to the restaurant which is supposed to be connected to websocket all time.
However, sometimes the restaurant is disconnected somehow, so I am trying to keep the restaurant connected, and if disconnected then reconnect again automatically.
In react native restaurant side implementation i have the following code :
this is useWebSocketLite hook to handle connection, send, receive messages and retry connection to server when closed:
function useWebSocketLite({ socketUrl, retry: defaultRetry = 3, retryInterval = 1000 }) {
const [data, setData] = useState();
const [send, setSend] = useState(() => () => undefined);
const [retry, setRetry] = useState(defaultRetry);
const [readyState, setReadyState] = useState(false);
useEffect(() => {
const ws = new WebSocket(socketUrl);
ws.onopen = () => {
setReadyState(true);
setSend(() => {
return (data) => {
try {
const d = JSON.stringify(data);
ws.send(d);
return true;
} catch (err) {
return false;
}
};
});
ws.onmessage = (event) => {
const msg = formatMessage(event.data);
setData({ message: msg, timestamp: getTimestamp() });
};
};
ws.onclose = () => {
setReadyState(false);
if (retry > 0) {
setTimeout(() => {
setRetry((retry) => retry - 1);
}, retryInterval);
}
};
return () => {
ws.close();
};
}, [retry]);
return { send, data, readyState };
}
So based on this, every-time the connection is closed, the connection will retry again.
Besides, when a restaurant launches the app the following code will be implemented:
const ws = useWebSocketLite({
socketUrl: `wss://${url}/id=${user.user_id}&role=restaurant`
});
This useEffect to establish the connection:
useEffect(() => {
if (ws.readyState === true) {
setConnectionOpen(true);
}
}, [ws.readyState]);
and this useEffect to handle incoming messages
useEffect(() => {
if (ws.data) {
const message = ws.data;
//dispatch...
}
}, [ws.data]);
Express server implementation:
This is the code where i handle socket connections and messages in express server:
var webSockets = {}
function setupWebSocket(server) {
server.on('connection', (socket, req) => {
if (req) {
var clientId = req.url
let regexReplace = /[\[\]/]/g
let regex = /([^=#&]+)=([^?&#]*)/g,
params = {},
match;
while ((match = regex.exec(clientId))) {
params[decodeURIComponent(match[1]).replace(regexReplace, '')] = decodeURIComponent(match[2])
}
if (params.role === 'restaurant') {
webSockets[params.id] = socket
}
}
socket.on('message', data => {
let sData = JSON.parse(JSON.parse(data))
let {id, data} = sData.data
sendToClient(id, 'order', data)
})
socket.on('error', (err) => {
console.log(err)
})
socket.on('close', (code, req) => {
var clientId = req.url
let regexReplace = /[\[\]/]/g
let regex = /([^=#&]+)=([^?&#]*)/g,
params = {},
match;
while ((match = regex.exec(clientId))) {
params[decodeURIComponent(match[1]).replace(regexReplace, '')] = decodeURIComponent(match[2])
}
if (params.role === 'restaurant') {
delete webSockets[clientId]
console.log(`${webSockets[clientId]} disconnected with code ${code} !`);
}
});
});
// sends a message to a specific client
const sendToClient = (clientId, type, data = {}) => {
const payload = { type, data }
const messageToSend = JSON.stringify({ error: false, message: payload })
if (webSockets[clientId]) {
webSockets[clientId].send(messageToSend)
console.log(`${clientId} client notified with this order`)
} else {
console.log(`${clientId} websocket client is not connected.`)
}
}
}
So most of the time I get 13 websocket client is not connected. which means the restaurant has already been deleted from the webSockets object and its connection already closed.
Apologise for long question and hope someone can help me regarding this.

Answer 1

First of all, you should know that this is not a good practice of websockets, where you are forcing the client (the restaurant) to be connected.
Whatever, at the current state of your code, there is an illogical behavior: at the end of the useEffect of your “useWebSocketLite” function, you are closing the socket connection:
return () => {
ws.close();
};
Knowing that the useEffect hook is called twice: after the first render of the component, and then after every change of the dependencies (the “retry” state in your case); Your code can be ridden like so: everytime the “retry” state changes, we will close the socket! So for me that is why you got the client disconnected.