Fix RTU data race

server.go

@@ -4,6 +4,7 @@ package mbserver
 import (
 	"io"
 	"net"
+	"sync"
 
 	"github.com/goburrow/serial"
 )
@@ -14,6 +15,8 @@ type Server struct {
 	Debug            bool
 	listeners        []net.Listener
 	ports            []serial.Port
+	portsWG          sync.WaitGroup
+	portsCloseChan   chan struct{}
 	requestChan      chan *Request
 	function         [256](func(*Server, Framer) ([]byte, *Exception))
 	DiscreteInputs   []byte
@@ -49,6 +52,8 @@ func NewServer() *Server {
 	s.function[16] = WriteHoldingRegisters
 
 	s.requestChan = make(chan *Request)
+	s.portsCloseChan = make(chan struct{})
+
 	go s.handler()
 
 	return s
@@ -94,6 +99,10 @@ func (s *Server) Close() {
 	for _, listen := range s.listeners {
 		listen.Close()
 	}
+
+	close(s.portsCloseChan)
+	s.portsWG.Wait()
+
 	for _, port := range s.ports {
 		port.Close()
 	}

servertu.go

@@ -15,13 +15,25 @@ func (s *Server) ListenRTU(serialConfig *serial.Config) (err error) {
 		log.Fatalf("failed to open %s: %v\n", serialConfig.Address, err)
 	}
 	s.ports = append(s.ports, port)
-	go s.acceptSerialRequests(port)
+
+	s.portsWG.Add(1)
+	go func() {
+		defer s.portsWG.Done()
+		s.acceptSerialRequests(port)
+	}()
+
 	return err
 }
 
 func (s *Server) acceptSerialRequests(port serial.Port) {
 	SkipFrameError:
 	for {
+		select {
+		case <-s.portsCloseChan:
+			return
+		default:
+		}
+
 		buffer := make([]byte, 512)
 
 		bytesRead, err := port.Read(buffer)