Delphi DLL

Open a direct-tcpip Channel (SSH Port Forwarding)

Demonstrates the Chilkat Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel through the SSH server to a target host and port. The first argument is the target hostname and the second is the target port. It returns the channel number, or -1 on failure.

Background: This is SSH local port forwarding at the API level: the channel carries ordinary TCP traffic to a service that may be reachable only from the SSH server's network — a database, an internal web app, a message broker. The key detail is that the server resolves the target name, not your machine, so it must resolve and be reachable there. Supplying a numeric IPv4 address avoids remote DNS resolution entirely.

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var
success: Boolean;
ssh: HCkSsh;
sshPort: Integer;
password: PWideChar;
targetHostname: PWideChar;
targetPort: Integer;
channelNum: Integer;

begin
success := False;

//  Demonstrates the Ssh.OpenDirectTcpIpChannel method, which opens a direct-tcpip channel
//  through the SSH server to a target host and port.  The 1st argument is the target hostname
//  and the 2nd is the target port.  It returns the channel number, or -1 on failure.

ssh := CkSsh_Create();

sshPort := 22;
success := CkSsh_Connect(ssh,'ssh.example.com',sshPort);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    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 := CkSsh_AuthenticatePw(ssh,'mySshLogin',password);
if (success = False) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

//  The target name is resolved by the SSH server, not by this computer, so it must be
//  reachable from the server's network.
targetHostname := 'db.internal.example.com';
targetPort := 5432;
channelNum := CkSsh_OpenDirectTcpIpChannel(ssh,targetHostname,targetPort);
if (channelNum < 0) then
  begin
    Memo1.Lines.Add(CkSsh__lastErrorText(ssh));
    Exit;
  end;

Memo1.Lines.Add('Opened direct-tcpip channel: ' + IntToStr(channelNum));

//  The channel now carries ordinary TCP data to the target, tunneled over SSH.

CkSsh_Disconnect(ssh);

CkSsh_Dispose(ssh);