Golang server, how to receive TCP JSON packet? - json

Question

I'm new to Golang and am using the "Server" code here as a starting point: http://www.golang-book.com/13/index.htm#section7
I've attempted to use JSON instead of Gob decoding (since I am required to write the client in C#), and I'm sending the JSON TCP data client data in a separate script from the code below.
I'm stuck on the part where I'm actually receiving the JSON TCP data and storing it in a variable for it to be decoded. It looks like I can decode it with json.Unmarshal, but I can't find any examples where json.Unmarshal is being used to decode TCP data. I can only find examples where json.Unmarshal is being used to decode JSON strings.
My code is below:
package main
import (
"encoding/json"
"fmt"
"net"
)
type coordinate struct {
X float64 `json:"x"`
Y float64 `json:"y"`
Z float64 `json:"z"`
}
func server() {
// listen on a port
ln, err := net.Listen("tcp", ":9999")
if err != nil {
fmt.Println(err)
return
}
for {
// accept a connection
c, err := ln.Accept()
if err != nil {
fmt.Println(err)
continue
}
// handle the connection
go handleServerConnection(c)
}
}
func handleServerConnection(c net.Conn) {
// receive the message
var msg coordinate
Stuck on the line below. What could I set the rawJSON variable equal to?
err := json.Unmarshal([]byte(rawJSON), &msg)
if err != nil {
fmt.Println(err)
} else {
fmt.Println("Received", msg)
}
c.Close()
}
func main() {
go server()
//let the server goroutine run forever
var input string
fmt.Scanln(&input)
}

Answer 1

You can patch a json.Decoder directly to the connection:
func handleServerConnection(c net.Conn) {
// we create a decoder that reads directly from the socket
d := json.NewDecoder(c)
var msg coordinate
err := d.Decode(&msg)
fmt.Println(msg, err)
c.Close()
}