C or C++ with libevent/libev: monitor a unix socket

Question

I'm trying to monitor a unix socket ("/tmp/mysocket").

I can do this fine in Node.js: it raises an event when

1. a socket is bound
2. someone connects to the socket
3. data is sent to the socket and
4. the socket is disconnected.

I'm trying to now do this in C/C++: I want to monitor "/tmp/mysocket" for the above events. I've looked at libevent (which I'd preferably like to use), but see that it requires an IP:port. Is there any way to monitor unix sockets?

Or can anyone suggest another C/C++ solution?

Answer 1

You could monitor a UNIX domain socket just like a regular file, since it can be operated like a file, e.g. in libev,

struct sockaddr_un address;
memset(&address, 0, sizeof(address));
address.sun_family = AF_LOCAL;
strcpy(address.sun_path, "/tmp/mysocket");

bind(socket, (struct sockaddr*)(&address), sizeof(address));
listen(socket, 5);

// now listen if someone has connected to the socket.
// we use 'ev_io' since the 'socket' can be treated as a file descriptor.
struct ev_io* io = malloc(sizeof(ev_io));
ev_io_init(io, accept_cb, socket, EV_READ);
ev_io_start(loop, io);
...

void accept_cb(struct ev_loop* loop, struct ev_io* io, int r)
{
    // someone has connected. we accept the child.
    struct sockaddr_un client_address;
    socklen_t client_address_len = sizeof(client_address);
    int client_fd = accept(socket, (sockaddr*)(&client_address),
                           &client_address_len);

    // 'read' / 'recv' from client_fd here.
    // or use another 'ev_io' for async read.
}

libevent should be similar.