Chilkat2-Python

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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import sys
import chilkat2

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.

ssh = chilkat2.Ssh()

sshPort = 22
success = ssh.Connect("ssh.example.com",sshPort)
if (success == False):
    print(ssh.LastErrorText)
    sys.exit()

# 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"

success = ssh.AuthenticatePw("mySshLogin",password)
if (success == False):
    print(ssh.LastErrorText)
    sys.exit()

channelNum = ssh.OpenSessionChannel()
if (channelNum < 0):
    print(ssh.LastErrorText)
    sys.exit()

success = ssh.SendReqExec(channelNum,"ls -l /tmp")
if (success == False):
    print(ssh.LastErrorText)
    sys.exit()

# 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):
    print(ssh.LastErrorText)
    sys.exit()

# Find out how much is waiting before retrieving it.
numBytes = ssh.GetReceivedNumBytes(channelNum)
if (numBytes < 0):
    print("Invalid channel, or its resources were already released.")
    sys.exit()

print("Bytes available: " + str(numBytes))

output = ssh.GetReceivedText(channelNum,"utf-8")
if (ssh.LastMethodSuccess == False):
    print(ssh.LastErrorText)
    sys.exit()

print(output)

ssh.Disconnect()