React Native Requires Chilkat v11.0.0+

IMAP Use Existing SSH Tunnel

Demonstrates how to connect to an IMAP server using an existing SSH tunnel. This creates a new channel within the SSH tunnel, which can be a TCP or TLS connection, and is connected to a remote IMAP server through port forwarding. React Native

import { Email, Imap, Socket } from '@chilkat/react-native'

async function chilkatExample() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  const tunnel = new Socket();

  const sshHostname = 'sftp.example.com';
  const sshPort = 22;

  // Connect to an SSH server and establish the SSH tunnel:
  try {
    await tunnel.sshOpenTunnelAsync(sshHostname, sshPort);
  } catch {
    console.log(tunnel.lastErrorText);
    return;
  }

  // Authenticate with the SSH server via a login/password
  // or with a public key.  
  // This example demonstrates SSH password authentication.
  // Note: This is not authenticating with the IMAP server, it is
  // for authenticating with the SSH server, which is separate.
  try {
    await tunnel.sshAuthenticatePwAsync('mySshLogin', 'mySshPassword');
  } catch {
    console.log(tunnel.lastErrorText);
    return;
  }

  // OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
  // Once the channel is obtained, the Socket API may
  // be used exactly the same as usual, except all communications
  // are sent through the channel in the SSH tunnel.
  // Any number of channels may be created from the same SSH tunnel.
  // Multiple channels may coexist at the same time.

  const imap = new Imap();

  // Let the IMAP object also use the SSH tunnel
  try {
    imap.useSshTunnel(tunnel);
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Connect to an IMAP server via the already established SSH tunnel.
  // Because the SSH tunnel has been previously setup,
  // this does not establish a direct connection with the IMAP
  // server.  It directs the SSH server to establish the connection.

  // In this example, the IMAP server requires SSL/TLS.  The TLS connection
  // will be enclosed within the SSH tunnel.
  imap.ssl = true;
  imap.port = 993;
  try {
    await imap.connectAsync('imap.my-imap-server.com');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Authenticate with the IMAP server via the SSH tunnel.
  try {
    await imap.loginAsync('myLogin', 'myPassword');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Select an IMAP mailbox
  try {
    await imap.selectMailboxAsync('Inbox');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // How many messages in Inbox?
  const msgCount = imap.numMessages;
  if (msgCount === 0) {
    console.log('No messages found.');
    return;
  }

  let upperBound = 10;
  if (msgCount < upperBound) {
    upperBound = msgCount;
  }

  // Download up to the 1st 10 messages.
  const email = new Email();
  const bUid = false;
  for (let i = 1; i <= upperBound; i++) {

    try {
      await imap.fetchEmailAsync(false, i, bUid, email);
    } catch {
      console.log(imap.lastErrorText);
      return;
    }

    console.log(email.from);
    console.log(email.subject);
  }

  // Disconnect from the IMAP server.
  // The SSH tunnel remains open.
  try {
    await imap.disconnectAsync();
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // It is possible to re-use the existing SSH tunnel for the next connection:
  try {
    await imap.connectAsync('imap.my-imap-server2.com');
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Review the LastErrorText to see that the connection was made via the SSH tunnel:
  console.log(imap.lastErrorText);

  // This closes the SSH channel, which is the connection with the IMAP server.
  // It does not close the SSH tunnel
  try {
    await imap.disconnectAsync();
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // Finally, close the SSH tunnel.

  // Note: If other objects are using the same SSH tunnel, the tunnel is not 
  // actually closed.  It is only closed when the last object using the tunnel closes it.

  // At this point, both the imap and tunnel objects have references to the internal
  // SSH tunnel.  We need to close each.

  // This call doesn't actually close the tunnel yet, because the tunnel object still
  // holds an internal reference.
  try {
    await imap.sshCloseTunnelAsync();
  } catch {
    console.log(imap.lastErrorText);
    return;
  }

  // This actually closes the SSH tunnel because it's the last object using it.
  try {
    await tunnel.sshCloseTunnelAsync();
  } catch {
    console.log(tunnel.lastErrorText);
    return;
  }

  console.log('IMAP pre-existing SSH tunnel example completed.');
}