Node.js

Get the Number of Bytes Buffered on an SSH Channel

Demonstrates the Chilkat Ssh.GetReceivedNumBytes method, which returns how many bytes are currently available in a channel's normal receive buffer. The only argument is the channel number. It returns -1 when the channel number is invalid or its retained resources have been released.

Background: This is a non-consuming look at how much is waiting, useful for deciding whether to retrieve now or keep reading, and for reporting progress on a large transfer. It counts only the normal receive buffer — bytes in the separate stderr buffer are excluded when StderrToStdout is false. Note that data received earlier can remain available even after a disconnect, so a positive count does not imply the connection is still up.

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Node.js

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function chilkatExample() {

    var success = false;

    //  Demonstrates the Ssh.GetReceivedNumBytes method, which returns the number of bytes currently
    //  available in a channel's normal receive buffer.  The only argument is the channel number.
    //  It returns -1 for an invalid channel or one whose resources have been released.

    var ssh = new chilkat.Ssh();

    var sshPort = 22;
    success = ssh.Connect("ssh.example.com",sshPort);
    if (success == false) {
        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.
    var password = "mySshPassword";

    success = ssh.AuthenticatePw("mySshLogin",password);
    if (success == false) {
        console.log(ssh.LastErrorText);
        return;
    }

    var channelNum = ssh.OpenSessionChannel();
    if (channelNum < 0) {
        console.log(ssh.LastErrorText);
        return;
    }

    success = ssh.SendReqExec(channelNum,"ls -l /tmp");
    if (success == false) {
        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;

    success = ssh.ChannelReceiveToClose(channelNum);
    if (success == false) {
        console.log(ssh.LastErrorText);
        return;
    }

    //  Find out how much is waiting before retrieving it.
    var numBytes = ssh.GetReceivedNumBytes(channelNum);
    if (numBytes < 0) {
        console.log("Invalid channel, or its resources were already released.");
        return;
    }

    console.log("Bytes available: " + numBytes);

    var output = ssh.GetReceivedText(channelNum,"utf-8");
    if (ssh.LastMethodSuccess == false) {
        console.log(ssh.LastErrorText);
        return;
    }

    console.log(output);

    ssh.Disconnect();

}

chilkatExample();