(CkPython) TCP Socket through SSH Tunnel (Port Forwarding)

Demonstrates using Chilkat Socket to communicate to a TCP service through an SSH tunnel. This example will connect to an NIST time server and (using the old Time Protocol (RFC 868)), will read the current GMT time.

Note: This is not necessarily a recommended means for getting the current date/time. The most commonly used time protocol is the Network Time Protocol (RFC-1305). The intent of this example is to show how TCP communications can occur through an SSH tunnel.

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import sys
import chilkat

# This example requires the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

tunnel = chilkat.CkSocket()

sshHostname = "sftp.example.com"
sshPort = 22

# Connect to an SSH server and establish the SSH tunnel:
success = tunnel.SshOpenTunnel(sshHostname,sshPort)
if (success != True):
    print(tunnel.lastErrorText())
    sys.exit()

# Authenticate with the SSH server via a login/password
# or with a public key.
# This example demonstrates SSH password authentication.
success = tunnel.SshAuthenticatePw("mySshLogin","mySshPassword")
if (success != True):
    print(tunnel.lastErrorText())
    sys.exit()

# OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
# Once the channel is obtained, the Socket API may
# be used exactly the same as usual, except all communications
# are sent through the channel in the SSH tunnel.
# Any number of channels may be created from the same SSH tunnel.
# Multiple channels may coexist at the same time.

# Connect to an NIST time server and read the current date/time

maxWaitMs = 4000
useTls = False
# channel is a CkSocket
channel = tunnel.SshOpenChannel("time-c.nist.gov",37,useTls,maxWaitMs)
if (tunnel.get_LastMethodSuccess() == False):
    print(tunnel.lastErrorText())
    sys.exit()

# The time server will send a big-endian 32-bit integer representing
# the number of seconds since since 00:00 (midnight) 1 January 1900 GMT.
# The ReceiveInt32 method will receive a 4-byte integer, but returns
# True or False to indicate success.  If successful, the integer
# is obtained via the ReceivedInt property.
bigEndian = True
success = channel.ReceiveInt32(bigEndian)
if (success != True):
    print(channel.lastErrorText())

    sys.exit()

dt = chilkat.CkDateTime()
dt.SetFromNtpTime(channel.get_ReceivedInt())

# Show the current local date/time
bLocalTime = True
print("Current local date/time: " + dt.getAsRfc822(bLocalTime))

# Close the SSH channel.
success = channel.Close(maxWaitMs)
if (success != True):
    print(channel.lastErrorText())

    sys.exit()

# It is possible to create a new channel from the existing SSH tunnel for the next connection:
# Any number of channels may be created from the same SSH tunnel.
# Multiple channels may coexist at the same time.
# channel is a CkSocket
channel = tunnel.SshOpenChannel("time-a.nist.gov",37,useTls,maxWaitMs)
if (tunnel.get_LastMethodSuccess() == False):
    print(tunnel.lastErrorText())
    sys.exit()

# Review the LastErrorText to see that the connection was made via the SSH tunnel:
print(tunnel.lastErrorText())

# Close the connection to time-a.nist.gov.  This is actually closing our channel
# within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
success = channel.Close(maxWaitMs)
if (success != True):
    print(channel.lastErrorText())

    sys.exit()

# Finally, close the SSH tunnel.
success = tunnel.SshCloseTunnel()
if (success != True):
    print(tunnel.lastErrorText())
    sys.exit()

print("TCP SSH tunneling example completed.")