Get the Number of Bytes Buffered on an SSH Channel

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Demonstrates the Chilkat Ssh.GetReceivedNumBytes method, which returns how many bytes are currently available in a channel's normal receive buffer. The only argument is the channel number. It returns -1 when the channel number is invalid or its retained resources have been released.

Background: This is a non-consuming look at how much is waiting, useful for deciding whether to retrieve now or keep reading, and for reporting progress on a large transfer. It counts only the normal receive buffer — bytes in the separate stderr buffer are excluded when StderrToStdout is false. Note that data received earlier can remain available even after a disconnect, so a positive count does not imply the connection is still up.

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#include <C_CkSsh.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkSsh ssh;
    int sshPort;
    const char *password;
    int channelNum;
    int numBytes;
    const char *output;

    success = FALSE;

    //  Demonstrates the Ssh.GetReceivedNumBytes method, which returns the number of bytes currently
    //  available in a channel's normal receive buffer.  The only argument is the channel number.
    //  It returns -1 for an invalid channel or one whose resources have been released.

    ssh = CkSsh_Create();

    sshPort = 22;
    success = CkSsh_Connect(ssh,"ssh.example.com",sshPort);
    if (success == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    //  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) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    channelNum = CkSsh_OpenSessionChannel(ssh);
    if (channelNum < 0) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    success = CkSsh_SendReqExec(ssh,channelNum,"ls -l /tmp");
    if (success == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    //  IMPORTANT: Set a read timeout.  ReadTimeoutMs defaults to 0, which means no limit -- without
    //  it, this call waits forever if the server never sends channel close.
    CkSsh_putReadTimeoutMs(ssh,15000);

    success = CkSsh_ChannelReceiveToClose(ssh,channelNum);
    if (success == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    //  Find out how much is waiting before retrieving it.
    numBytes = CkSsh_GetReceivedNumBytes(ssh,channelNum);
    if (numBytes < 0) {
        printf("Invalid channel, or its resources were already released.\n");
        CkSsh_Dispose(ssh);
        return;
    }

    printf("Bytes available: %d\n",numBytes);

    output = CkSsh_getReceivedText(ssh,channelNum,"utf-8");
    if (CkSsh_getLastMethodSuccess(ssh) == FALSE) {
        printf("%s\n",CkSsh_lastErrorText(ssh));
        CkSsh_Dispose(ssh);
        return;
    }

    printf("%s\n",output);

    CkSsh_Disconnect(ssh);


    CkSsh_Dispose(ssh);

    }