CkPython

Get Received SSH Bytes into a BinData

Demonstrates the Chilkat Ssh.GetReceivedBd method, which appends the bytes currently in a channel's normal receive buffer to a BinData. The first argument is the channel number and the second is the BinData. The channel receive buffer is cleared afterward; existing bytes in the BinData are preserved.

Background: When the remote command emits binary — a tarball, an image, a compressed stream — decoding it as text through a charset would corrupt it. BinData keeps the bytes exactly as received, so you can write them to a file, hash them, or hand them to another API. Like the StringBuilder form it appends, making it easy to accumulate across successive reads. On failure the BinData is left unchanged.

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import sys
import chilkat

success = False

#  Demonstrates the Ssh.GetReceivedBd method, which appends the bytes currently in a channel's
#  receive buffer to a BinData.  The 1st argument is the channel number and the 2nd is the
#  BinData.  The channel receive buffer is cleared afterward.

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()

#  Run a command whose output may be binary.
success = ssh.SendReqExec(channelNum,"cat /usr/bin/hostname")
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()

#  Append the raw received bytes to a BinData.  Existing bytes in the BinData are preserved.
bd = chilkat.CkBinData()
success = ssh.GetReceivedBd(channelNum,bd)
if (success == False):
    print(ssh.lastErrorText())
    sys.exit()

print("Bytes received: " + str(bd.get_NumBytes()))

ssh.Disconnect()