No timeout in RTU Server causes some sort of deadlock #19
Description
I'm trying to test out the RTU Server.
If I specify a timeout, the server is unstable: it either times out before the client connects or closes if requests are not made often enough.
If I don't specify a timeout, the server seems to work great, but calling Close seems to block forever and I can't cleanly shut it down.
With timeout speciffied
package main
import (
"os"
"os/signal"
"time"
"github.com/goburrow/serial"
"github.com/tbrandon/mbserver"
)
func main() {
serv := mbserver.NewServer()
err := serv.ListenRTU(&serial.Config{
Address: "/dev/ttyUSB0",
BaudRate: 115200,
DataBits: 8,
StopBits: 1,
Parity: "N",
Timeout: 10 * time.Second})
if err != nil {
panic(err)
}
println("Server is running...")
defer func() {
println("Stopping server...")
serv.Close()
println("Server stopped")
os.Exit(0)
}()
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt)
<-c
}Output
$ go run main.go
Server is running...
2024/09/10 16:52:10 serial read error serial: timeout
^CStopping server...
Server stoppedNote that I was able to read/write several coils with no problem. But if I wait longer than the timeout period to issue another command, I get the serial read error, and all subsequent requests to the server fail. However, I am able to close the server down cleanly.
Without timeout
package main
import (
"os"
"os/signal"
"github.com/goburrow/serial"
"github.com/tbrandon/mbserver"
)
func main() {
serv := mbserver.NewServer()
err := serv.ListenRTU(&serial.Config{
Address: "/dev/ttyUSB0",
BaudRate: 115200,
DataBits: 8,
StopBits: 1,
Parity: "N"})
if err != nil {
panic(err)
}
println("Server is running...")
defer func() {
println("Stopping server...")
serv.Close()
println("Server stopped")
os.Exit(0)
}()
c := make(chan os.Signal, 1)
signal.Notify(c, os.Interrupt)
<-c
}$ go run main.go
Server is running...
^CStopping server...
signal: terminatedI am able to read/write many times, with large gaps in between with no issues. Note that the server only shuts down cleanly now when a kill <pid> is issued. The program hangs on serv.Close().
It seems there is some sort of deadlock here. I noticed in the docs a section on Race Conditions, however I'm not doing anything with goroutines here and the version with a timeout works just fine.