How to deal with Bad User Input and Socket Connection Errors

Question

I am creating a socket that will take user input for the connection. Ideally because with user input there is inherently error involved i want to beable to handle the cases where the socket can not connect to the desired Address:Port combo.

Using the node.js "Net" API I can easilly create a client socket connection to the server. We will create a function that allows for user input to the socket

function createConnection(HOST,PORT){
    let socket = new net.Socket();
    socket.connect(PORT, HOST, function() {
        console.log('CONNECTED TO: ' + HOST + ':' + PORT);
        socket.write(SomeData)
    }
    socket.on("data", (data) => {
        console.log("data")
    })
    socket.on("error", (err) => {
        console.log(err," This Error Occured!")
    })
    socket.on("close", () => {
        console.log("Closing Connection")
    })
}

Then we can call that function to create a socket connection with user defined parameters. My issue is that whether I wrap the function in a try catch as follows

try{
    createConnection(userInputedHost, userInputedPort)
} catch (error) {
    console.log(error, "This Error Occured!")
}

to handle a connection error or if i use the error event defined in the socket creation i am never able to see the string "This Error Occured!" and instead have my console flooded with the default exception

node:events:505
      throw er; // Unhandled 'error' event
      ^

Error: connect ECONNREFUSED 127.0.0.1:3977
    at TCPConnectWrap.afterConnect [as oncomplete] (node:net:1187:16)
Emitted 'error' event on Socket instance at:
    at emitErrorNT (node:internal/streams/destroy:157:8)
    at emitErrorCloseNT (node:internal/streams/destroy:122:3)
    at processTicksAndRejections (node:internal/process/task_queues:83:21) {
  errno: -4078,
  code: 'ECONNREFUSED',
  syscall: 'connect',
  address: '127.0.0.1',
  port: 3977
}

Am I not using try catch blocks correctly, am I not understanding the error event form the net API? Is there a way to handle an improper connection request without casing the node app to crash?

Eric Olsen · Accepted Answer · 2023-02-22 14:40:17Z

0

The Awnser is to use

socket.on("error", (err) => {
        console.log(err," This Error Occured!")
    })

as described in this post. I had been implementing the proper use of the event but my issue was i was not compiling properly. I was going form .ts -> .js and had my tsconfig set wrong so none of the changes i made were being pushed to the js file. A closer inspection of the compiled js file showed that the error event code was never added in. Once solved everything works as intended

answered Feb 22, 2023 at 14:40

Eric Olsen

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