The unhandledRejection event is emitted whenever a promise rejection is not handled. "Rejection" is the canonical term for a promise reporting an error. As defined in ES6, a promise is a state machine representation of an asynchronous operation and can be in one of 3 states: "pending", "fulfilled", or "rejected". Somebody decided that JavaScript programmers couldn't be trusted with managing promise rejections properly and changed the HTML spec to require browsers to throw "unhandled promise rejection" errors if a rejected promise has no rejection handlers added before code returns to the event loop. The error usually happens in async await functions, and there’s an easy fix.

const functionName = async (arguments) => {
try {
// Your code here
} catch (error) {
// Handle rejection here
}
};

Your Java socket shows SocketTimeoutException means that it takes too long to get respond from other device and your request expires before getting response. This exception is occurring on following condition.

• Server is slow and default timeout is less, so just put timeout value according to you.
• Server is working fine but timeout value is for less time. so change the timeout value.

Solution: A developer can pre-set the timeout option for both client and server operations.

From Client side:

Socket socket = new Socket();
SocketAddress socketAddress = new InetSocketAddress(host, port);
socket.connect(socketAddress, 12000); //12000 are milli seconds

From Server side:

ServerSocket serverSocket = new new ServerSocket(port);
serverSocket.setSoTimeout(12000);

It seems like toFixed() is a better solution, but it is not! In some cases it will NOT round correctly. Also, Math.round() will NOT round correctly in some cases.

To correct the rounding problem with the previous Math.round() and toFixed(), you can define a custom JavaScript rounding function that performs a "nearly equal" test to determine whether a fractional value is sufficiently close to a midpoint value to be subject to midpoint rounding. The following function return the value of the given number rounded to the nearest integer accurately.

Number.prototype.roundTo = function(decimal) {
return +(Math.round(this + "e+" + decimal) + "e-" + decimal);
}

var num = 9.7654;
console.log( num.roundTo(2)); //output 9.77