Visual FoxPro

Wait for a Message on Any SSH Channel

Demonstrates the Chilkat Ssh.WaitForChannelMessage method, which waits for the next SSH channel message on any channel. The only argument is the poll timeout: 0 for a nonblocking check, a positive value to wait that long, or a negative value to wait with no method-level timeout. It returns the channel number the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error such as a lost connection.

Background: When several channels are active at once, waiting on one specific channel would block while others sit ready. This method is the multiplexed alternative — it returns as soon as any channel has activity and tells you which one, so a single loop can service them all. The explicit timeout argument governs the wait; shorter ReadTimeoutMs values do not cut it short.

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Visual FoxPro

LOCAL lnSuccess
LOCAL loSsh
LOCAL lnSshPort
LOCAL lcPassword
LOCAL lnChannelNum
LOCAL lnPollTimeoutMs
LOCAL lnResult

lnSuccess = 0

*  Demonstrates the Ssh.WaitForChannelMessage method, which waits for the next SSH channel
*  message on ANY channel.  The only argument is the poll timeout in milliseconds: 0 for a
*  nonblocking check, a positive value to wait that long, or a negative value to wait with no
*  method-level timeout.

loSsh = CreateObject('Chilkat.Ssh')

lnSshPort = 22
lnSuccess = loSsh.Connect("ssh.example.com",lnSshPort)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
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.
lcPassword = "mySshPassword"

lnSuccess = loSsh.AuthenticatePw("mySshLogin",lcPassword)
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnChannelNum = loSsh.OpenSessionChannel()
IF (lnChannelNum < 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

lnSuccess = loSsh.SendReqExec(lnChannelNum,"ls -l /tmp")
IF (lnSuccess = 0) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

*  Wait up to 5 seconds for the next channel message.  The return value is the channel number
*  the message belongs to, -1 if nothing arrived before the timeout, or -2 on another error.
lnPollTimeoutMs = 5000
lnResult = loSsh.WaitForChannelMessage(lnPollTimeoutMs)

IF (lnResult = -2) THEN
    ? loSsh.LastErrorText
    RELEASE loSsh
    CANCEL
ENDIF

IF (lnResult = -1) THEN
    ? "No channel message arrived before the timeout."
ENDIF

IF (lnResult >= 0) THEN
    ? "Processed a message for channel " + STR(lnResult)
ENDIF

loSsh.Disconnect()

RELEASE loSsh