Multiple tcp connections in single thread with using libevent or boost::asio. It's possible?

Question

Is it possible to use libevent for create multiple tcp connections to different servers in one thread? Could you write a sample implementation of such a task?

I have done so, but not sure that it's right:

...
int num_of_connect = 5; /*for example*/
struct event_base *evbase;
struct bufferevent *bev[num_of_connect];
struct sockaddr_in sin[num_of_connect];
evbase = event_base_new();

for(int i=0;i<=(num_of_connect-1);i++){

   sin[i].sin_family = AF_INET;
   sin[i].sin_addr.s_addr = inet_addr(/*some addr*/);
   sin[i].sin_port = htons(/*some port*/);

   bev[i] = bufferevent_socket_new(evbase, -1, BEV_OPT_CLOSE_ON_FREE);

   bufferevent_setcb(bev[i], cb_evread, cb_evwrite, cb_event, NULL);
   bufferevent_socket_connect(bev[i], (struct sockaddr *)&sin[i], sizeof(struct sockaddr_in));
}

event_base_dispatch(evbase);
...

In addition, similar can be implemented using the boost::asio? Example?)

Answer 1

In addition, similar can be implemented using the boost::asio? Example?)

Yes, it is entirely possible. This is the basis of the proactor design pattern promoted by Boost.Asio. It achieves concurrency without the use of explicit threads by avoiding blocking operations such as connect , accept , read , and write . You might find some of my previous answers useful here

• Proactor and async_write
• Clarification about asynchronous and synchronous operations

As Tony pointed out in his answer , the Boost.Asio has fantastic examples explaining the asynchronous concepts in detail. The tutorial, specifically the asynchronous daytime server , is also a good place to start.

Answer 2

You could use boost::asio to run in a thread which accepts the connection asynchronously. There is examples on the boost::asio documentation page which will show you how to setup a server which accepts multiple connections on a single thread.

I'm not familiar with libevent to help you there.

Answer 3

Is it possible to use libevent for create multiple tcp connections to different servers in one thread? Could you write a sample implementation of such a task?

Yes, its possible.

You could also create a server that listened on multiple ports with evconnlistener_new_bind .

And if you wanted to handle one or more signals, then you could use evsignal_new to add signals to the event base.

In each case ( bufferevent_socket_new , evconnlistener_new_bind and evsignal_new , the callbacks for each event would be likely different.