Created
August 5, 2020 06:14
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package main | |
import ( | |
"encoding/binary" | |
"fmt" | |
"log" | |
"net" | |
"syscall" | |
"time" | |
) | |
func main() { | |
addrChan := make(chan *net.UDPAddr) | |
go func() { | |
log.Fatal(runServer(addrChan)) | |
}() | |
if err := runClient(<-addrChan); err != nil { | |
log.Fatal(err) | |
} | |
} | |
func setSockOpt(conn *net.UDPConn) error { | |
rawConn, err := conn.SyscallConn() | |
if err != nil { | |
return err | |
} | |
return rawConn.Control(func(fd uintptr) { | |
if err := syscall.SetsockoptInt(int(fd), syscall.IPPROTO_IP, syscall.IP_PKTINFO, 1); err != nil { | |
panic(err) | |
} | |
}) | |
} | |
func runServer(addrChan chan<- *net.UDPAddr) error { | |
laddr, err := net.ResolveUDPAddr("udp4", "localhost:0") | |
if err != nil { | |
return err | |
} | |
conn, err := net.ListenUDP("udp4", laddr) | |
if err != nil { | |
return err | |
} | |
if err := setSockOpt(conn); err != nil { | |
return err | |
} | |
addrChan <- conn.LocalAddr().(*net.UDPAddr) | |
for { | |
b := make([]byte, 1000) | |
oob := make([]byte, 0, 1000) | |
n, oobn, flags, addr, err := conn.ReadMsgUDP(b, oob) | |
if err != nil { | |
return err | |
} | |
fmt.Println("Received packet:") | |
fmt.Printf("\tn: %d, oobn: %d, flags: %d, addr: %s\n", n, oobn, flags, addr) | |
fmt.Printf("\toob: %#x\n", oob[:oobn]) | |
} | |
} | |
func runClient(raddr *net.UDPAddr) error { | |
laddr, err := net.ResolveUDPAddr("udp4", "localhost:0") | |
if err != nil { | |
return err | |
} | |
conn, err := net.ListenUDP("udp4", laddr) | |
if err != nil { | |
return err | |
} | |
if err := setSockOpt(conn); err != nil { | |
return err | |
} | |
for i := 0; i < 5; i++ { | |
b := make([]byte, 8) | |
binary.BigEndian.PutUint64(b, uint64(i)) | |
if _, _, err := conn.WriteMsgUDP(b, nil, raddr); err != nil { | |
return err | |
} | |
time.Sleep(200 * time.Millisecond) | |
} | |
return nil | |
} |
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