Poll Event Loop Sample in C++

The Poll Event Loop sample demonstrates how to add HTTP server functionality to your C application and use a polled event loop to wait for I/O events. AppWeb offers several methods to wait for events. See the Programming Paradigms document for further information.

The sample is a single-threaded main program that listens on port 8888 for HTTP requests. See also the equivalent C pollEventLoop sample.

Files

pollEventLoop.conf
pollEventLoop.cpp

Configuration File

pollEventLoop.conf

DocumentRoot "."
Listen 8888
ThreadLimit 0

LoadModule ejs ../../../lib/libejsModule
LoadModule egi ../../../lib/libegiHandler
LoadModule esp ../../../lib/libespHandler
LoadModule static ../../../lib/libcopyHandler

AddHandler egiHandler .egi
AddHandler espHandler .esp
AddHandler copyHandler 

This configuration file loads the embedded javascript module and the embedded server pages and embedded gateway interface, and static content handlers. It is configured to run single-threaded. It assumes that the sample is being run from the C/pollEventLoop directory. Modify these module paths to suit your installation.

You should modify the DocumentRoot and Listen directives to suit your application's needs.

Source Code

pollEventLoop.cpp

//
//  Copyright (c) Mbedthis Software LLC, 2003-2004. All Rights Reserved.
//
/// @file   pollEventLoop.cpp
/// @brief  Embed the AppWeb server in a single-threaded program using
///         a polled event loop.
///
                                                                                
/////////////////////////////// Includes ///////////////////////////////
                                                                                
#include    "appWeb/appWeb.h"
                                                                                
//////////////////////////// Forward Declarations //////////////////////
                                                                                
static void eventLoop();
                                                                                
/////////////////////////////////// Code ///////////////////////////////
                                                                                
int main(int argc, char** argv)
{
    MaHttp      *http;                  // Http service inside our app
    MaServer    *server;                // For the HTTP server
    Mpr         mpr("pollEventLoop");   // Initialize the run time
                                                                                
#if MPR_FEATURE_LOG
    //
    //  Do the following two statements only if you want debug trace
    //
    mpr.addListener(new MprLogToFile());
    mpr.setLogSpec("stdout:4");
#endif
                                                                                
    //
    //  Start the Mbedthis Portable Runtime and request single threading
    //
    mpr.start(0);
                                                                                
    //
    //  Create Http and Server objects for this application. We set the
    //  ServerName to be "default" and the initial serverRoot to be ".".
    //  This will be overridden in pollEventLoop.conf.
    //
    http = new MaHttp();
    server = new MaServer(http, "default", ".");
                                                                                
    //
    //  Configure the server with the configuration directive file
    //
    if (server->configure("pollEventLoop.conf", 0) < 0) {
        mprFprintf(MPR_STDERR,
            "Can't configure the server. Error on line %d\n",
            server->getLine());
        exit(2);
    }
                                                                                
    //
    //  Start the server
    //
    if (http->start() < 0) {
        mprFprintf(MPR_STDERR, "Can't start the server\n");
        exit(2);
    }
                                                                                
    //
    //  Service incoming requests until time to exit.
    //
    eventLoop();
                                                                                
    //
    //  Orderly shutdown
    //
    http->stop();
    delete server;
    delete http;
                                                                                
    //
    //  MPR run-time will automatically stop and be cleaned up
    //
    return 0;
}
                                                                                
////////////////////////////////////////////////////////////////////////
//
//  Sample polled event loop. This demonstrates how to integrate AppWeb
//  with your applications event loop using a polling architecture.
//
                                                                                
static void eventLoop()
{
    Mpr             *mpr;
    int         till, timeout;
                                                                                
    mpr = mprGetMpr();
                                                                                
    //
    //  We will nap for 50 milliseconds to avoid busy waiting
    //
    timeout = 50;
                                                                                
    while (!mpr->isExiting()) {
                                                                                
        mpr->runTimers();
        till = mpr->getIdleTime();
                                                                                
        //
        //  Run any queued tasks
        //
        if (mpr->runTasks() > 0) {          // Returns > 0 if more work to do
            till = 0;                       // So don't block in serviceEvents
        }
                                                                                
        //
        //  Do some work here
        //
                                                                                
                                                                                
        //
        //  Now service any pending I/O
        //
        mpr->serviceEvents(1, min(timeout, till));
    }
}