PHP

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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<?php

use Chilkat2\Ssh;

// 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.

$ssh = new Ssh();

$sshPort = 22;
try {
    $ssh->Connect('ssh.example.com', $sshPort);

    // 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.
    $password = 'mySshPassword';

    $ssh->AuthenticatePw('mySshLogin', $password);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

$channelNum = $ssh->OpenSessionChannel();
if ($channelNum < 0) {
    echo $ssh->LastErrorText, "\n";
    exit;
}

try {
    $ssh->SendReqExec($channelNum, 'ls -l /tmp');

    // 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;

    $ssh->ChannelReceiveToClose($channelNum);
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

// Find out how much is waiting before retrieving it.
$numBytes = $ssh->GetReceivedNumBytes($channelNum);
if ($numBytes < 0) {
    echo "Invalid channel, or its resources were already released.\n";
    exit;
}

echo 'Bytes available: ', $numBytes, "\n";

try {
    $output = $ssh->GetReceivedText($channelNum, 'utf-8');
} catch (\Chilkat2\Exception $e) {
    echo $e->getMessage(), "\n";
    exit;
}

echo $output, "\n";

$ssh->Disconnect();