maeqtt/main.go

package main

import (
	"log"
	"net"
	"runtime/debug"

	"badat.dev/maeqtt/v2/mqtt/packets"
	"badat.dev/maeqtt/v2/session"
)

func main() {
	listenAddr := ":1883"
	listener, err := net.Listen("tcp", listenAddr)

	if err != nil {
		log.Fatalf("Coulde't start a listener on tcp %v. Error: %e", listenAddr, err)
	}

	var sessions map[string]*session.Session = make(map[string]*session.Session)
	removeSessChan := make(session.RemoveSessionChannel)
	connChan := make(chan net.Conn)

	go func() {
		for {
			conn, err := listener.Accept()
			if err != nil {
				log.Println("Failed accepting connection ", err)
			} else {
				connChan <- conn
			}
		}

	}()

	for {
		select {
		case con := <-connChan:
			handleConnection(con, sessions, removeSessChan)
		case sesID := <-removeSessChan:
			delete(sessions, sesID)
		}
	}
}

func handleConnection(con net.Conn, sessions map[string]*session.Session, rmSessChan session.RemoveSessionChannel) {
	defer handlePanic(con)

	conReq, err := session.NewConnection(con)
	if err != nil {
		log.Println("Failed to create connection  ", err)
		return
	}

	var sess *session.Session
	if conReq.ConnectPakcet.ClientId != nil {
		exists := false
		sess, exists = sessions[*conReq.ConnectPakcet.ClientId]
		if exists {
			log.Printf("Resuming session %v", *sess.ClientID)
			sess.ConnecionChannel <- conReq
		}
	}

	if sess == nil {
		newSess := session.NewSession(conReq, rmSessChan)
		sess = &newSess
		sessions[*sess.ClientID] = sess
		log.Printf("New session %v", *sess.ClientID)
		go func() {
			defer handlePanic(con)
			sess.HandlerLoop()
		}()
	}
}

func handlePanic(con net.Conn) {
	if r := recover(); r != nil {
		log.Println("Recovering from panic:", r)
		log.Println("Stack Trace:")
		debug.PrintStack()

		err := packets.DisconnectPacket{
			ReasonCode: packets.DisconnectReasonCodeImplErorr,
		}.Write(con)
		if err != nil {
			log.Println("Failed to send a disconnect packet after recovering from panic", err)
		}
	}
}