B4X Requires Chilkat v11.0.0+

TCP Socket through SSH Tunnel (Port Forwarding)

See more Socket/SSL/TLS Examples

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.

B4X

Dim success As Boolean = False

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

Dim tunnel As ChilkatSocket
tunnel.Initialize("tunnel")

Dim sshHostname As String = "sftp.example.com"
Dim sshPort As Int = 22

'  Connect to an SSH server and establish the SSH tunnel:
success = tunnel.SshOpenTunnel(sshHostname, sshPort)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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 = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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
Dim maxWaitMs As Int = 4000
Dim useTls As Boolean = False
Dim channel As ChilkatSocket
channel.Initialize("channel")
success = tunnel.SshNewChannel("time-c.nist.gov", 37, useTls, maxWaitMs, channel)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  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.
Dim bigEndian As Boolean = True
success = channel.ReceiveInt32(bigEndian)
If success = False Then
    Log(channel.LastErrorText)
    Return
End If


Dim dt As ChilkatDateTime
dt.Initialize
dt.SetFromNtpTime(channel.ReceivedInt)

'  Show the current local date/time
Dim bLocalTime As Boolean = True
Log("Current local date/time: " & dt.GetAsRfc822(bLocalTime))

'  Close the SSH channel.
success = channel.Close(maxWaitMs)
If success <> True Then
    Log(channel.LastErrorText)
    Return
End If


'  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.
success = tunnel.SshNewChannel("time-a.nist.gov", 37, useTls, maxWaitMs, channel)
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


'  Review the LastErrorText to see that the connection was made via the SSH tunnel:
Log(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 Then
    Log(channel.LastErrorText)
    Return
End If


'  Finally, close the SSH tunnel.
success = tunnel.SshCloseTunnel
If success = False Then
    Log(tunnel.LastErrorText)
    Return
End If


Log("TCP SSH tunneling example completed.")