How do you use the net functions effectively in Go? - network-programming

Question

For example, having basic packet protocol, like:
[packetType int][packetId int][data []byte]
And making a client and server doing simple things with it (egx, chatting.)

Answer 1

Here's a client and server with sloppy panic error-handling. They have some limitations:
The server only handles one client connection at a time. You could fix this by using goroutines.
Packets always contain 100-byte payloads. You could fix this by putting a length in the packet somewhere and not using encoding/binary for the entire struct, but I've kept it simple.
Here's the server:
package main
import (
"encoding/binary"
"fmt"
"net"
)
type packet struct {
// Field names must be capitalized for encoding/binary.
// It's also important to use explicitly sized types.
// int32 rather than int, etc.
Type int32
Id int32
// This must be an array rather than a slice.
Data [100]byte
}
func main() {
// set up a listener on port 2000
l, err := net.Listen("tcp", ":2000")
if err != nil {
panic(err.String())
}
for {
// start listening for a connection
conn, err := l.Accept()
if err != nil {
panic(err.String())
}
handleClient(conn)
}
}
func handleClient(conn net.Conn) {
defer conn.Close()
// a client has connected; now wait for a packet
var msg packet
binary.Read(conn, binary.BigEndian, &msg)
fmt.Printf("Received a packet: %s\n", msg.Data)
// send the response
response := packet{Type: 1, Id: 1}
copy(response.Data[:], "Hello, client")
binary.Write(conn, binary.BigEndian, &response)
}
Here's the client. It sends one packet with packet type 0, id 0, and the contents "Hello, server". Then it waits for a response, prints it, and exits.
package main
import (
"encoding/binary"
"fmt"
"net"
)
type packet struct {
Type int32
Id int32
Data [100]byte
}
func main() {
// connect to localhost on port 2000
conn, err := net.Dial("tcp", ":2000")
if err != nil {
panic(err.String())
}
defer conn.Close()
// send a packet
msg := packet{}
copy(msg.Data[:], "Hello, server")
err = binary.Write(conn, binary.BigEndian, &msg)
if err != nil {
panic(err.String())
}
// receive the response
var response packet
err = binary.Read(conn, binary.BigEndian, &response)
if err != nil {
panic(err.String())
}
fmt.Printf("Response: %s\n", response.Data)
}

Answer 2

Check out Jan Newmarch's "Network programming with Go".