In continuous Encode calls, the Decode peer receive zero value

[zhliner]

type Args struct {
	A, B int
}
type Request struct {
	ID     uint64
	Method string
}
// msgp EncodeMsg & DecodeMsg done.

---

client.go

func main() {
	conn, err := net.Dial("tcp", "127.0.0.1:1234")
	if err != nil {
		log.Fatal("dialing:", err)
	}
	ids := Request{1, "Arith.Divide"}
	args := Args{int('z'), int('a')}
	args2 := Args{int('x'), int('i')}

	msgp.Encode(conn, ids)
	// log.Println("hai")  // If this is valid, the server's result is ok.
	msgp.Encode(conn, args)
	msgp.Encode(conn, args2)
}

---

server.go

func main() {
	l, e := net.Listen("tcp", ":1234")
	if e != nil {
		log.Fatal("listen error:", e)
	}
	fmt.Println("start listen for client...")
	for {
		conn, err := l.Accept()
		if err != nil {
			log.Print("rpcjs.Serve: accept:", err.Error())
			return
		}
		var req Request
		var arg Args
		var arg2 Args
		msgp.Decode(conn, &req)
		fmt.Println(req)

		msgp.Decode(conn, &arg)
		fmt.Println(arg)

		msgp.Decode(conn, &arg2)
		fmt.Println(arg2)
	}
}

// Output: client first run
{1 Arith.Divide}
{0 0} or {120 105} or {122 97}
{0 0}

// Output: client second run
{1 Arith.Divide}
{122 97}
{0 0}

why?
when the log.Println("hai") is valid, the calls is ok.
// Output:
{1 Arith.Divide}
{122 97}
{120 105}

[zhliner]

on Windows 10 x64 os

[shabbyrobe]

I can replicate this on OS X.

To solve your immediate problem, use the same msgp.Reader and call DecodeMsg on your structs directly:

rd := msgp.NewReader(conn)
(&req).DecodeMsg(rd)
fmt.Println(req)

(&arg).DecodeMsg(rd)
fmt.Println(arg)

(&arg2).DecodeMsg(rd)
fmt.Println(arg2)

The underlying problem with the msgp.Decode API you're using seems to be that it may create a new msgp.Reader for every call to msgp.Decode, but if multiple messages are queued on the socket when the msgp.Reader reads from it, those bytes are discarded when the call to msgp.Decode completes.

I really don't have a good idea off the top of my head how to solve that problem, but at the very least, avoiding those APIs in favour of the msgp.NewReader example I posted earlier should help get you moving.

[zhliner]

@shabbyrobe
In fact, I want to use msgp as a net/rpc Codec. But directly use of DecodeMsg seem not so good.
however, thank you!!

And thanks for translate.google.com ^,^