Ruby

SSH Tunnel (Port Forwarding via direct-tcpip Channel)

Demonstrates creating an SSH tunnel to a remote host:port using a direct-tcpip channel. Data written to the channel is forwarded by the SSH server to the target, and data read back is whatever the target sent. This example tunnels a simple HTTP GET request to a web server.

Background: This is SSH local port forwarding at the API level, and the target need not be a web server — it can be a database, a message broker, or any TCP service. The key detail is that the SSH server resolves and connects to the target, not your machine, so the destination only has to be reachable from the server's network. That is what makes tunneling useful for reaching services behind a firewall. Note the receive pattern here: read until the double CRLF that ends an HTTP header, extract exactly that with GetReceivedTextS, then poll briefly for the body, which may already have arrived.

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Ruby

require 'chilkat'

success = false

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

#  Demonstrates creating an SSH tunnel to a remote host:port using a direct-tcpip channel.
#  Data written to the channel is forwarded by the SSH server to the target host:port, and data
#  read from the channel is whatever the target sent back.

ssh = Chilkat::CkSsh.new()

hostname = "ssh.example.com"
port = 22
success = ssh.Connect(hostname,port)
if (success == false)
    print ssh.lastErrorText() + "\n";
    exit
end

#  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() + "\n";
    exit
end

#  Ask the SSH server to connect onward to this host:port.  The target is resolved by the SSH
#  server, not by this computer, so it must be reachable from the server's network.  The target
#  need not be a web server -- it can be any TCP service.
targetHost = "www.chilkatsoft.com"
targetPort = 80
channelNum = ssh.OpenDirectTcpIpChannel(targetHost,targetPort)
if (channelNum < 0)
    print ssh.lastErrorText() + "\n";
    exit
end

#  Send a simple HTTP GET request through the tunnel.
httpReq = "GET /xyz123.html HTTP/1.1\r\nHost: www.chilkatsoft.com\r\n\r\n"
success = ssh.ChannelSendString(channelNum,httpReq,"utf-8")
if (success == false)
    print ssh.lastErrorText() + "\n";
    exit
end

#  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
#  which means no limit -- without it, this call waits forever if the received data never
#  contains a match.
ssh.put_ReadTimeoutMs(15000)

#  An HTTP response header ends with a blank line, so receive until a double CRLF is seen.
#  The method may read beyond the match, but it stops waiting as soon as the match appears.
caseSensitive = false
matchStr = "\r\n\r\n"
success = ssh.ChannelReceiveUntilMatch(channelNum,matchStr,"utf-8",caseSensitive)
if (success == false)
    print ssh.lastErrorText() + "\n";
    exit
end

#  GetReceivedTextS removes everything through and including the match, which is exactly the
#  response header.
responseHeader = ssh.getReceivedTextS(channelNum,matchStr,"utf-8")
if (ssh.get_LastMethodSuccess() == false)
    print ssh.lastErrorText() + "\n";
    exit
end

print "---- HTTP Response Header ----" + "\n";
print responseHeader + "\n";

#  The body may already have arrived along with the header.  Poll briefly for anything more.
#  A -2 return simply means nothing further arrived, which is not an error here.
pollTimeoutMs = 200
numBytesRead = ssh.ChannelPoll(channelNum,pollTimeoutMs)
if (numBytesRead == -1)
    print ssh.lastErrorText() + "\n";
    exit
end

htmlBody = ssh.getReceivedText(channelNum,"utf-8")
if (ssh.get_LastMethodSuccess() == false)
    print ssh.lastErrorText() + "\n";
    exit
end

print "---- HTML BODY ----" + "\n";
print htmlBody + "\n";

success = ssh.ChannelSendClose(channelNum)
if (success == false)
    print ssh.lastErrorText() + "\n";
    exit
end

ssh.Disconnect()