Java

Check Whether an SSH Channel is Open

Demonstrates the Chilkat Ssh.ChannelIsOpen method, which reports whether a channel number identifies a channel Chilkat currently considers open for application I/O. The only argument is the channel number. This example checks the channel before and after sending CLOSE.

Background: Because one SSH connection can carry many channels with independent lifetimes, code that manages several needs a way to ask whether a given one is still usable. This returns false for invalid or nonexistent channel numbers, after a local Disconnect, once remote closure is processed, and immediately after ChannelSendClose — which marks the channel locally closed without waiting for the remote side.

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Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  Demonstrates the Ssh.ChannelIsOpen method, which reports whether a channel number identifies
    //  a channel Chilkat currently considers open for application I/O.  The only argument is the
    //  channel number.

    CkSsh ssh = new CkSsh();

    int sshPort = 22;
    success = ssh.Connect("ssh.example.com",sshPort);
    if (success == false) {
        System.out.println(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.
    String password = "mySshPassword";

    success = ssh.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    //  Open a session channel.  A negative return value indicates failure.
    int channelNum = ssh.OpenSessionChannel();
    if (channelNum < 0) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    if (ssh.ChannelIsOpen(channelNum)) {
        System.out.println("The channel is open.");
        }
    else {
        System.out.println("The channel is not open.");
        }

    //  Send CLOSE, which immediately marks the channel locally closed.
    success = ssh.ChannelSendClose(channelNum);
    if (success == false) {
        System.out.println(ssh.lastErrorText());
        return;
        }

    if (ssh.ChannelIsOpen(channelNum)) {
        System.out.println("Still open.");
        }
    else {
        System.out.println("The channel is now closed.");
        }

    ssh.Disconnect();
  }
}