We need to install boost library on Ubuntu:

$ $ cat /proc/version
Linux version 3.11.0-12-generic (buildd@allspice) (gcc version 4.8.1 (Ubuntu/Linaro 4.8.1-10ubuntu7) ) #19-Ubuntu SMP Wed Oct 9 16:20:46 UTC 2013

$ sudo apt-get install libboost-all-dev

Here is the list of installed boost libraries:

libboost_atomic
libboost_chrono
libboost_context
libboost_date_time
libboost_filesystem
libboost_graph_parallel
libboost_graph
libboost_iostreams
libboost_locale
libboost_math_c99f
libboost_math_c99l
libboost_math_c99
libboost_math_tr1f
libboost_math_tr1l
libboost_math_tr1
libboost_mpi_python-py27
libboost_mpi_python-py33
libboost_mpi_python
libboost_mpi
libboost_prg_exec_monitor
libboost_program_options
libboost_python-py27
libboost_python-py33
libboost_python
libboost_random
libboost_regex
libboost_serialization
libboost_signals
libboost_system
libboost_thread
libboost_timer
libboost_unit_test_framework
libboost_wave
libboost_wserialization

The asio classes can be used by including the asio.hpp header file.

The following example will print out "Blocking wait()..." in 0, 1, 2, 3, and 4 second intervals by using a timer synchronously. That is, the call to wait() will not return until the timer has expired.

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

int main()
{
  boost::asio::io_service io;
 
  for(int i = 0; i < 5; i++) {
    boost::asio::deadline_timer timer(io, boost::posix_time::seconds(i));
    timer.wait();
    std::cout << "Blocking wait(): " << i << " second-wait\n";
  }

  return 0;
}

Makefile looks like this:

sync_timer: sync_timer.o
        g++ -o sync_timer sync_timer.o -lboost_system -lboost_thread -lpthread
sync_timer.o: sync_timer.cpp
        g++ -c sync_timer.cpp
clean:
        rm -f *.o sync_timer

Output:

$ make
g++ -c sync_timer.cpp
g++ -o sync_timer sync_timer.o  -L /usr/lib -lboost_system -lboost_thread -lpthread

$ ./sync_timer
Blocking wait(): 0 second-wait
Blocking wait(): 1 second-wait
Blocking wait(): 2 second-wait
Blocking wait(): 3 second-wait
Blocking wait(): 4 second-wait

• To use timers, the Boost.Date_Time header file is included.
• We declared an io_service object io:

  boost::asio::io_service io;
  

• we declared an object of type boost::asio::deadline_timer.
• The asio classes that provide I/O (in this case timer) take a reference to an io_service as their first argument. The second argument sets the timer to expire in i seconds.

  boost::asio::deadline_timer t(io, boost::posix_time::seconds(i));
  

• We used a blocking wait on the timer. In other words, the call to deadline_timer::wait() will not return until the timer has expired.

The following code demonstrates how to use asio's asynchronous callback functionality and how to perform an asynchronous wait on the timer.

#include <iostream>
#include <boost/asio.hpp>
#include <boost/date_time/posix_time/posix_time.hpp>

void work_for_io_service(const boost::system::error_code& /*e*/)
{
  std::cout << "Non-blocking wait() \n";
}

int main()
{
  boost::asio::io_service io;

  boost::asio::deadline_timer timer(io, boost::posix_time::seconds(5));

  // work_for_io_service() will be called 
  // when async operation (async_wait()) finishes  
  // note: Though the async_wait() immediately returns
  //       but the callback function will be called when time expires
  timer.async_wait(&work_for_io_service);

  std::cout << "If we see this before the callback function, we know async_wait() returns immediately\n. This confirms async_wait() is non-blocking call!\n";

  // the callback function, work_for_io_service(), will be called 
  // from the thread where io.run() is running. 
  io.run();

  return 0;
}