(MFC) Bidirectional Sockets (TLS or non-TLS, simultaneous reading and writing a connection)

This example demonstrates how to simultaneously read/write on a single socket connection.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkSocket.h>
#include <CkTask.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkSocket tlsRead;

    // We'll just use an HTTPS server for this example...
    bool bUseTls = true;
    int maxWaitMs = 5000;
    bool success = tlsRead.Connect("www.chilkatsoft.com",443,bUseTls,maxWaitMs);
    if (success != true) {
        strOut.append(tlsRead.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Chilkat classes are thread-safe.  This means that only one method call can be active
    // at a time for a given object instance.  It would seem that this would prevent the possibility
    // to simultaneously read/write a given connection because it would require two method calls
    // to be simultaneously active: one for reading and one for writing.
    // 
    // There's a trick to doing it...
    // 
    // The CloneSocket method is provided to get a new object instance that shares the same socket
    // connection.  This allows for the coarse-grained object-level thread safety to be maintained, 
    // while finer-grained thread-safety mechanisms keep things kosher internally.

    // One object will be used for reading, and the cloned socket is used for writing.
    // It doesn't matter which --  you can use the cloned socket for reading or the original for writing.
    // However.. if you try to read simultneously from both the original and cloned objects at the same
    // time, then one will block until the other finishes.  (This is because of the finer-grained thread
    // safety internally.)  The same is true if you try to write both socket objects simultaneously.

    CkSocket *tlsWrite = tlsRead.CloneSocket();

    // Let's start an async read on the socket.  Nothing will be arriving until we actually send the GET
    // request and the server responds.  This will read until the end of the HTTP response header.
    CkTask *task = tlsRead.ReceiveUntilMatchAsync("\r\n\r\n");
    task->Run();

    // Now send the request.  This should not block because the read is happening on the tlsRead object.
    const char *httpGetReq = "GET / HTTP/1.1\r\nHost: www.chilkatsoft.com\r\n\r\n";
    success = tlsWrite->SendString(httpGetReq);
    // Assuming success for the example...

    // Wait for the read task to finish.
    // The true/false returned by Wait applies to the Wait method call, not the task.
    maxWaitMs = 5000;
    success = task->Wait(maxWaitMs);
    if (!success || (task->get_StatusInt() != 7) || (task->get_TaskSuccess() != true)) {
        if (!success) {
            // The task.LastErrorText applies to the Wait method call.
            strOut.append(task->lastErrorText());
            strOut.append("\r\n");
        }
        else {
            // The ResultErrorText applies to the underlying task method call (i.e. the Connect)
            strOut.append(task->status());
            strOut.append("\r\n");
            strOut.append(task->resultErrorText());
            strOut.append("\r\n");
        }

        delete task;
        delete tlsWrite;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Examine the received HTTP response header:
    strOut.append("HTTP response header:");
    strOut.append("\r\n");
    strOut.append(task->getResultString());
    strOut.append("\r\n");

    // We should get a response that looks like this:
    // 	HTTP response header:
    // 	HTTP/1.1 200 OK
    // 	Cache-Control: private
    // 	Content-Length: 7477
    // 	Content-Type: text/html
    // 	Server: Microsoft-IIS/8.5
    // 	Set-Cookie: ASPSESSIONIDSWDSTRTQ=BBNMIKGCHFJNILFFPLDIOGDE; secure; path=/
    // 	X-Powered-By: ASP.NET
    // 	X-Powered-By-Plesk: PleskWin
    // 	Date: Thu, 06 Apr 2017 12:03:30 GMT

    delete task;
    delete tlsWrite;

    // Forget about the remainder of the HTTP response... The example was only to demonstrate
    // simultaneous reading/writing..
    maxWaitMs = 20;
    tlsRead.Close(maxWaitMs);


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }