在GO中使用UDP进行RPC

Question

Unity3D networking libraries use UDP and has methods for RPC calls. I'm trying to get my server to use RPC over UDP and I'm having some trouble. Here's the basic server code I've got now:

type Args struct {
  X, Y int
}

type RequestHandler struct{}

func (self *RequestHandler) Add(args *Args, reply *int) error {
  *reply = args.X + args.Y
  return nil
}

func main() {
  addr := net.UDPAddr{ Port: 5127, IP: net.ParseIP("127.0.0.1") } 
  handler := new(RequestHandler)

  rpc.Register(handler)
  conn, err := net.ListenUDP("udp", &addr)
  defer conn.Close()

  if err != nil {
    panic(err)
  }

  for {
    go rpc.ServeConn(conn)
  }
}

And here is the client code:

type Args struct {
  X, Y int
}

func main() {
  client, err := rpc.Dial("udp", "127.0.0.1:5127")
  if err != nil { log.Fatal("dialing:", err) }

  // Synchronous call
  args := &Args{7,8}
  var reply int
  err = client.Call("RequestHandler.Add", args, &reply)
  if err != nil {
    log.Fatal("arith error:", err)
  }

  fmt.Printf("Result: %d + %d = %d", args.X, args.Y, reply)
}

When I run these, they both just hang, nothing happens. What am I doing wrong?

Answer 1

RPC over UDP requires special UDP aware handling due to the nature of UDP sockets.

There is no connection, just datagrams sent to an address.

For the client to get a reply, it would have to set up a listening socket and then send that to the server along with the request. The server would then reply to the clients address.

net/rpc doesn't have any special case handling for non-connection oriented transports (ie: UDP)

I don't know of any packages that implement connection-less RPC for go, so you may have to roll your own here.