CkPython

Check Whether SSH Channel CLOSE Was Received

Demonstrates the Chilkat Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message has been received for a channel. The only argument is the channel number. Remote CLOSE is distinct from EOF and closes the channel in both directions.

Background: Remote CLOSE is the definitive end of a channel's life. Once it is processed, ChannelIsOpen becomes false and the channel is normally removed from NumOpenChannels. Checking it distinguishes "the server finished sending output" (EOF) from "the channel is fully finished" (CLOSE) — which is what you want before concluding a remote command has completely wrapped up.

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import sys
import chilkat

success = False

#  Demonstrates the Ssh.ChannelReceivedClose method, which reports whether an SSH CLOSE message
#  has been received for a channel.  The only argument is the channel number.  Remote CLOSE is
#  distinct from EOF and closes the channel in both directions.

ssh = chilkat.CkSsh()

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.put_ReadTimeoutMs(15000)

success = ssh.ChannelReceiveToClose(channelNum)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

#  The server may send EOF before CLOSE.  During that interval EOF is True while CLOSE is
#  still False.
if (ssh.ChannelReceivedEof(channelNum)):
    print("EOF received.")

if (ssh.ChannelReceivedClose(channelNum)):
    print("Remote CLOSE received -- the channel is closed in both directions.")
else:
    print("No remote CLOSE received.")

ssh.Disconnect()