Xbase++

SSH Tunnel TCP Socket Options

Demonstrates tuning the underlying TCP socket with the SoRcvBuf, SoSndBuf, TcpNoDelay, OutboundBindIpAddress, and OutboundBindPort properties. These normally should be left at their defaults.

Background: These are low-level knobs for specific situations. Larger send/receive buffers can improve throughput on high-bandwidth, high-latency ("long fat") links; TcpNoDelay disables Nagle's algorithm to cut latency for small interactive packets at the cost of efficiency; and binding the outbound socket to a specific local address or port is occasionally required by firewall rules or multi-homed hosts. Change them only with a concrete reason, since the defaults are tuned for the common case.

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LOCAL nSuccess
LOCAL oTunnel
LOCAL nSshPort
LOCAL cPassword
LOCAL nListenPort
LOCAL nWaitForThreadExit

nSuccess := 0

//  Demonstrates tuning the underlying TCP socket with the SshTunnel properties SoRcvBuf, SoSndBuf,
//  TcpNoDelay, OutboundBindIpAddress, and OutboundBindPort.
//  
//  These normally should be left at their defaults; adjust them only for specific performance or
//  networking requirements.

oTunnel := CreateObject("Chilkat.SshTunnel")

//  Socket send/receive buffer sizes, in bytes.  Larger buffers can help throughput on
//  high-latency links.
oTunnel:SoRcvBuf := 4194304
oTunnel:SoSndBuf := 262144

//  Disable Nagle's algorithm to reduce latency for small, interactive packets.
oTunnel:TcpNoDelay := 1

//  Bind the outbound socket to a specific local address/port before connecting.  0 (the default)
//  lets the OS choose the local port; an empty address lets the OS choose the interface.
oTunnel:OutboundBindIpAddress := "192.168.1.50"
oTunnel:OutboundBindPort := 0

oTunnel:DestHostname := "db.internal.example.com"
oTunnel:DestPort := 5432

nSshPort := 22
nSuccess := oTunnel:Connect("ssh.example.com", nSshPort)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

//  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.
cPassword := "mySshPassword"

nSuccess := oTunnel:AuthenticatePw("mySshLogin", cPassword)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

nListenPort := 1080
nSuccess := oTunnel:BeginAccepting(nListenPort)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

? "Tunnel established with custom socket options."

nWaitForThreadExit := 1
nSuccess := oTunnel:CloseTunnel(nWaitForThreadExit)
IF (nSuccess == 0)
    ? oTunnel:LastErrorText
    oTunnel:destroy()
    RETURN
ENDIF

oTunnel:destroy()