React Native

Release an SSH Channel's Local Resources

Demonstrates the Chilkat Ssh.ChannelRelease method, which releases Chilkat's retained local resources for a channel after all output and exit information has been retrieved. The only argument is the channel number.

Background: Chilkat retains a channel's buffered output and exit information after the channel closes, so you can still read a command's final output. That retention costs memory, and a long-running program that opens many channels should release each one when finished with it. Note this is not a channel-closing method — it sends neither EOF nor CLOSE. Retrieve everything you need first, because releasing discards it.

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React Native

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

async function chilkatExample() {
  // Demonstrates the Ssh.ChannelRelease method, which releases Chilkat's retained local resources
  // for a channel after all output and exit information has been retrieved.  The only argument is
  // the channel number.

  const ssh = new Ssh();

  const sshPort = 22;
  try {
    await ssh.connectAsync('ssh.example.com', sshPort);
  } 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;
  }

  // Open a session channel.  A negative return value indicates failure.
  const channelNum = await ssh.openSessionChannelAsync();
  if (channelNum < 0) {
    console.log(ssh.lastErrorText);
    return;
  }

  try {
    await ssh.sendReqExecAsync(channelNum, 'uname -a');
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

  // IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
  // it, this call waits forever if the server never sends channel close.
  ssh.readTimeoutMs = 15000;

  // Retrieve everything of interest before releasing the channel.
  try {
    await ssh.channelReceiveToCloseAsync(channelNum);
  } catch {
    console.log(ssh.lastErrorText);
    return;
  }

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

  console.log(output);

  // Release the retained local resources.  This does not send EOF or CLOSE.
  ssh.channelRelease(channelNum);

  ssh.disconnect();
}