rkravchik / listeners

Listeners with keep alive and notifications.

Net Listeners

TCPKeepAliveListener

TCPKeepAliveListener is a copy of the non-exportable respective struct from net/http.

Sometimes it is needed to check port to listen not in http.ListenAndServe(address).

Of course one can do something like this:

l, err := net.Listen("tcp", addr)
if err != nil {
    // ...
}
// some stuff
// ...
http.Serve(l)

But if we look at http.Server.ListenAndServe() a little closer we will see:

ln, err := net.Listen("tcp", addr)
if err != nil {
    return err
}
return srv.Serve(tcpKeepAliveListener{ln.(*net.TCPListener)})

And that's why if you want:

1. try to listen port before http.Serve;
2. keep-alive timeouts on accepted connections;

you have to use listeners like TCPKeepAliveListener.

Simple usage example:

package main
 
import "github.com/rkravchik/listeners"
 
func main() {
    // ...
    addr, err := net.ResolveTCPAddr("tcp", address)
    if err != nil {
        // ...
    }
    l, err := net.ListenTCP("tcp", addr)
    if err != nil {
        // ...
    }
    err = http.Serve(listeners.TCPKeepAliveListener{TCPListener: l})
    // ...
}

DoListener

DoListener is a net.TCPListener with keep-alive timeouts and ability to execute the given func on first accept being called. Use it like:

package main
     
import "github.com/rkravchik/listeners"
 
func main() {
    // ...
    addr, err := net.ResolveTCPAddr("tcp", address)
    if err != nil {
        // ...
    }
    l, err := net.ListenTCP("tcp", addr)
    if err != nil {
        // ...
    }
    dl := NewDoListener(l).OnFirstAcceptDo(func() {fmt.Println("i'm ready to accept")})
    err = http.Serve(dl)
    // ...
}