Binding do privileged ports.This example shows, how to use a BindHelper in order to bind to privileged ports. Before trying this, the bindhelper binary must be changed setuid-root.
/* $Id: ehs_privport.cpp 121 2012-04-05 22:39:22Z felfert $
 *
 * EHS is a library for embedding HTTP(S) support into a C++ application
 *
 * Copyright (C) 2004 Zachary J. Hansen
 *
 * Code cleanup, new features and bugfixes: Copyright (C) 2010 Fritz Elfert
 *
 *    This library is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU Lesser General Public
 *    License version 2.1 as published by the Free Software Foundation;
 *
 *    This library is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *    Lesser General Public License for more details.
 *
 *    You should have received a copy of the GNU Lesser General Public
 *    License along with this library; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *    This can be found in the 'COPYING' file.
 *
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <ehs.h>
#include <sstream>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cerrno>

#ifdef HAVE_SYS_TYPES_H
# include <sys/types.h>
#endif
#ifdef HAVE_SYS_SOCKET_H
# include <sys/socket.h>
#endif
#ifdef HAVE_SYS_WAIT_H
# include <sys/wait.h>
#endif
#ifdef HAVE_NETINET_IN_H
# include <netinet/in.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif

#include "common.h"

using namespace std;

// subclass of EHS that defines a custom HTTP response.
class TestHarness : public EHS
{
    // generates a page for each http request
    ResponseCode HandleRequest ( HttpRequest * request, HttpResponse * response )
    {
        ostringstream oss;
        oss
            << "<html><head><title>TestHarness</title></head><body><table><tr>"
            << "<tr><td>request-method:</td><td>" << request->Method() << "</td></tr>" << endl
            << "<tr><td>uri:</td><td>" << request->Uri() << "</td></tr>" << endl
            << "<tr><td>http-version:</td><td>" << request->HttpVersion() << "</td></tr>" << endl
            << "<tr><td>body-length:</td><td>" << request->Body().length ( ) << "</td></tr>" << endl
            << "<tr><td>number-request-headers:</td><td>" << request->Headers().size ( ) << "</td></tr>" << endl
            << "<tr><td>number-form-value-maps:</td><td>" << request->FormValues().size ( ) << "</td></tr>" << endl
            << "<tr><td>client-address:</td><td>" << request->RemoteAddress ( ) << "</td></tr>" << endl
            << "<tr><td>client-port:</td><td>" << request->RemotePort ( ) << "</td></tr>" << endl;

        for ( StringMap::iterator i = request->Headers().begin ( );
                i != request->Headers().end ( ); i++ ) {
            oss << "<tr><td>Request Header:</td><td>" << i->first << " => " << i->second << "</td></tr>" << endl;
        }

        for ( CookieMap::iterator i = request->Cookies().begin ( );
                i != request->Cookies().end ( ); i++ ) {
            oss << "<tr><td>Cookie:</td><td>" << i->first << " => " << i->second << "</td></tr>" << endl;
        }
        oss << "</table></body></html>" << endl;

        response->SetBody ( oss.str().c_str(), oss.str().length() );
        return HTTPRESPONSECODE_200_OK;
    }
};

#ifndef _WIN32
// Bind helper is not needed on win32, because win32 does not
// have a concept of privileged ports.
class MyHelper : public PrivilegedBindHelper
{
    public:
        MyHelper() : mutex(pthread_mutex_t())
        {
            pthread_mutex_init(&mutex, NULL);
        }

        virtual bool BindPrivilegedPort(int socket, const char *addr, const unsigned short port)
        {
            bool ret = false;
            pid_t pid;
            int status;
            char buf[32];
            pthread_mutex_lock(&mutex);
            switch (pid = fork()) {
                case 0:
                    sprintf(buf, "%08x%08x%04x", socket, inet_addr(addr), port);
                    execl("bindhelper", buf, ((void *)NULL));
                    exit(errno);
                    break;
                case -1:
                    break;
                default:
                    if (waitpid(pid, &status, 0) != -1) {
                        ret = (0 == status);
                        if (0 != status)
                            cerr << "bind: " << strerror(WEXITSTATUS(status)) << endl;
                    }
                    break;
            }
            pthread_mutex_unlock(&mutex);
            return ret;
        }

    private:
        pthread_mutex_t mutex;
};
#endif

//   waits for RETURN while the EHS thread does its job.
int main ( int argc, char ** argv )
{
    cout << getEHSconfig() << endl;
    if (argc != 2) {
        cerr << "Usage: " << basename(argv[0]) << " [port]" << endl;
        return 0;
    }

    cerr << "binding to " << atoi(argv[1]) << endl;
    TestHarness srv;
#ifndef _WIN32
    MyHelper h;
    srv.SetBindHelper(&h);
#endif

    EHSServerParameters oSP;
    oSP["port"] = argv[1];
    oSP["mode"] = "threadpool";

    try {
        srv.StartServer(oSP);
        kbdio kbd;
        cout << "Press q to terminate ..." << endl;
        while (!(srv.ShouldTerminate() || kbd.qpressed())) {
            usleep(300000);
        }
        srv.StopServer();
    } catch (exception &e) {
        cerr << "ERROR: " << e.what() << endl;
    }

    return 0;
}