I have two programs, a listener and a dialer. I want a two way street of UDP communication on the same port. My Listener as expected reads the datagram sent from the dialer, then sends back 5 datagrams of its own. Only trouble is, my dialer isn't reading it.
I tried using net.DialUDP but when I use that, 0 datagrams get sent from the dialer.
listener - Works great
func main() {
addr := net.UDPAddr{
Port: 7000,
IP: net.ParseIP("127.0.0.1"),
}
conn, err := net.ListenUDP("udp", &addr)
defer conn.Close()
if err != nil {
panic(err)
}
i := 0
b := make([]byte, 10)
conn.ReadFromUDP(b)
fmt.Println(string(b[:]))
for i < 5 {
conn.WriteToUDP([]byte("sending back"), &addr)
i++
}
}
Dialer that sends datagram but cannot read them
func main() {
sock, _ := net.Dial("udp", "127.0.0.1:7000")
buf := make([]byte, 100)
_, werr := sock.Write([]byte("first send"))
if werr != nil {
fmt.Println(werr)
}
sock.Read(buf)
fmt.Println(string(buf[:]))
}
Dialer that doesn't send any datagrams
func main() {
remote, _ := net.ResolveUDPAddr("udp", "127.0.0.1:7000")
sock, _ := net.DialUDP("udp", nil, remote)
buf := make([]byte, 10)
for {
sock.WriteToUDP([]byte("first send"), remote)
sock.ReadFromUDP(buf)
fmt.Println(string(buf[:]))
}
}
When in doubt, just use ListenUDP. It will both send and receive datagrams.
sock, _ := net.Dial("udp", "127.0.0.1:7000")
This creates a net.Conn, which is only a basic connection interface. You have to assert it as a *net.UDPConn to get the actual UDP methods to work.
sock, _ := net.DialUDP("udp", nil, remote)
This creates a "connected" UDP socket, and uses the bare Write method to send to a single remote address.