Java

Multiple SendReqExec on the Same Connection

Demonstrates running a series of commands on one SSH connection using SendReqExec. Each exec request requires its own logical channel — this is not a separate SSH connection, just a new session channel on the existing one.

Background: An SSH session channel is single-use for an exec request: once the command runs and the server closes the channel, that channel cannot be reused. Opening a fresh channel per command is cheap, since the expensive work — the TCP connection, key exchange, and authentication — is done once and shared. This is why running ten commands over one connection is far faster than connecting ten times.

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import com.chilkatsoft.chilkat2.ChilkatException;
import com.chilkatsoft.chilkat2.Ssh;

public class ChilkatExample {

    public static void main(String[] args) {
        // This example requires the Chilkat API to have been previously unlocked.
        // See Global Unlock Sample for sample code.

        // Demonstrates running a series of commands on one SSH connection using SendReqExec.  Each exec
        // request requires its own logical channel.  This is not a new SSH connection -- it is simply a
        // new session channel on the existing one.

        Ssh ssh = new Ssh();

        String hostname = "ssh.example.com";
        int port = 22;
        try {
            ssh.connect(hostname, port);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            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";

        try {
            ssh.authenticatePw("mySshLogin", password);
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            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.setReadTimeoutMs(15000);

        // ---- 1st command, on its own session channel ----
        int channelNum = ssh.openSessionChannel();
        if (channelNum < 0) {
            System.out.println(ssh.getLastErrorText());
            return;
        }

        String cmdOutput;
        try {
            ssh.sendReqExec(channelNum, "ls -al");

            ssh.channelReceiveToClose(channelNum);

            cmdOutput = ssh.getReceivedText(channelNum, "utf-8");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println(cmdOutput);
        System.out.println("----");

        // ---- 2nd command, on a NEW session channel over the same connection ----
        channelNum = ssh.openSessionChannel();
        if (channelNum < 0) {
            System.out.println(ssh.getLastErrorText());
            return;
        }

        try {
            ssh.sendReqExec(channelNum, "nslookup chilkatsoft.com");

            ssh.channelReceiveToClose(channelNum);

            cmdOutput = ssh.getReceivedText(channelNum, "utf-8");
        } catch (ChilkatException e) {
            System.out.println(e.getLastErrorText());
            return;
        }

        System.out.println(cmdOutput);

        ssh.disconnect();
    }
}