SSH Tunnel (Port Forwarding via direct-tcpip Channel)

See more SSH Examples

Demonstrates creating an SSH tunnel to a remote host:port using a direct-tcpip channel. Data written to the channel is forwarded by the SSH server to the target, and data read back is whatever the target sent. This example tunnels a simple HTTP GET request to a web server.

import { Ssh } from '@chilkat/react-native'

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

  // Demonstrates creating an SSH tunnel to a remote host:port using a direct-tcpip channel.
  // Data written to the channel is forwarded by the SSH server to the target host:port, and data
  // read from the channel is whatever the target sent back.

  const ssh = new Ssh();

  const hostname = 'ssh.example.com';
  const port = 22;
  try {
    await ssh.connectAsync(hostname, port);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // Normally you would not hard-code the password in source.  You should instead obtain it
  // from an interactive prompt, environment variable, or a secrets vault.
  const password = 'mySshPassword';

  try {
    await ssh.authenticatePwAsync('mySshLogin', password);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // Ask the SSH server to connect onward to this host:port.  The target is resolved by the SSH
  // server, not by this computer, so it must be reachable from the server's network.  The target
  // need not be a web server -- it can be any TCP service.
  const targetHost = 'www.chilkatsoft.com';
  const targetPort = 80;
  const channelNum = await ssh.openDirectTcpIpChannelAsync(targetHost, targetPort);
  if (channelNum < 0) {
    console.log(ssh.lastErrorText);
    return;
  }

  // Send a simple HTTP GET request through the tunnel.
  const httpReq = 'GET /xyz123.html HTTP/1.1\r\nHost: www.chilkatsoft.com\r\n\r\n';
  try {
    await ssh.channelSendStringAsync(channelNum, httpReq, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
  // which means no limit -- without it, this call waits forever if the received data never
  // contains a match.
  ssh.readTimeoutMs = 15000;

  // An HTTP response header ends with a blank line, so receive until a double CRLF is seen.
  // The method may read beyond the match, but it stops waiting as soon as the match appears.
  const caseSensitive = false;
  const matchStr = '\r\n\r\n';
  try {
    await ssh.channelReceiveUntilMatchAsync(channelNum, matchStr, 'utf-8', caseSensitive);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // GetReceivedTextS removes everything through and including the match, which is exactly the
  // response header.
  let responseHeader: string;
  try {
    responseHeader = ssh.getReceivedTextS(channelNum, matchStr, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  console.log('---- HTTP Response Header ----');
  console.log(responseHeader);

  // The body may already have arrived along with the header.  Poll briefly for anything more.
  // A -2 return simply means nothing further arrived, which is not an error here.
  const pollTimeoutMs = 200;
  const numBytesRead = await ssh.channelPollAsync(channelNum, pollTimeoutMs);
  if (numBytesRead === -1) {
    console.log(ssh.lastErrorText);
    return;
  }

  let htmlBody: string;
  try {
    htmlBody = ssh.getReceivedText(channelNum, 'utf-8');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  console.log('---- HTML BODY ----');
  console.log(htmlBody);

  try {
    await ssh.channelSendCloseAsync(channelNum);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  ssh.disconnect();
}