net

TCP echo server

ln, err := net.Listen("tcp", ":8080")
if err != nil { log.Fatal(err) }
defer ln.Close()

for {
    conn, err := ln.Accept()
    if err != nil { log.Print(err); continue }
    go func(c net.Conn) {
        defer c.Close()
        io.Copy(c, c)
    }(conn)
}

Dial — make an outgoing connection

conn, err := net.Dial("tcp", "example.com:80")
if err != nil { log.Fatal(err) }
defer conn.Close()

fmt.Fprintf(conn, "GET / HTTP/1.0\r\n\r\n")
io.Copy(os.Stdout, conn)

Dialer — timeouts and keep-alive

net.Dial gives you a default dialer. Construct your own for timeouts, local address binding, or context cancellation.

d := &net.Dialer{Timeout: 5 * time.Second, KeepAlive: 30 * time.Second}
conn, err := d.DialContext(ctx, "tcp", "example.com:443")

Listen and read packets

pc, _ := net.ListenPacket("udp", ":9000")
defer pc.Close()

buf := make([]byte, 1500)
for {
    n, addr, _ := pc.ReadFrom(buf)
    fmt.Printf("%d bytes from %s: %s\n", n, addr, buf[:n])
}

LookupHost, LookupIP, LookupMX

ips, _ := net.LookupIP("example.com")
for _, ip := range ips {
    fmt.Println(ip)
}

SplitHostPort and JoinHostPort

host, port, _ := net.SplitHostPort("example.com:8080")
addr := net.JoinHostPort("::1", "8080")   // handles IPv6 brackets correctly