Catch error thrown after connection is rejected - Question

[JRobertsDS]

I have the following code to capture the fingerprint of a server for (server) testing.
I reject the connection after capturing the fingerprint by returning "false" from the hostVerifier.
Doing so causes an error (KEY_EXCHANGE_FAILED) that I would like to catch so that it doesn't propagate -- it's expected behavior in my testing environment.
But I am baffled as to how to catch this error, and am looking for ideas.

var Connection = require('ssh2');

function getSSHFingerprintSSH2(ip, port) {
  return new Promise(resolve => {
    let fingerprintToReturn = "fingerprint error";
    let sshConnection = new Connection();

    sshConnection.on('error', function() {
      //normal operation resolves here after rejecting the connection
      resolve(fingerprintToReturn);
    });
    sshConnection.connect({
      host: ip,
      port: port,
      username: '',
      password: '',
      hostHash: 'sha256',
      hostVerifier: function(fingerprint) {
        fingerprintToReturn = fingerprint;
        // returning "false" rejects the connection with a handshake error
        // which is what we want to do normally, having captured the fingerprint
        return false;
      },
    });
  });
}

[mscdex]

The code looks fine to me. Are you saying this code throws an error instead of being emitted under an 'error' event? If so, what is the exact error that you're seeing? Are you on the latest ssh2 v0.8.x?

[JRobertsDS]

I am using the latest, v.0.8.x.
The code itself is fine, the error, KEY_EXCHANGE_FAILED, is expected. My problem is that I don’t know how to catch the error so that I can prevent its writing to the console and appearing, in my test, to be a problem. Essentially, where can I try...catch to catch this error, which is thrown by SSH2 after my callback returns “false”?

[mscdex]

There should be no async throwing in ssh2/ssh2-streams, that's why I was curious as to exactly which error you were seeing (in the console) that was not being handled by your 'error' event handler.

[theophilusx]

In many cases, ssh2 reports errors using an error event. To 'catch' this, you need to add an error listener which will handle the event. You cannot use try/catch to catch events, only event listeners will work.

[JRobertsDS]

Thanks; I was missing the distinction between catching thrown errors and listening for error events.