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// This implements a simple example that can be tested on a machine
// running systemd.
package main
import (
"bufio"
"flag"
"fmt"
"log"
"net"
"os"
"os/signal"
"strings"
"sync"
"golang.org/x/sys/unix"
"go.awhk.org/gosdd"
)
var useNames = flag.Bool("use-names", false, "whether to use SDListenFDsWithNames or not")
func main() {
flag.Parse()
log.SetFlags(log.Lshortfile)
if !*useNames {
fds, err := gosdd.SDListenFDs(true)
if err != nil {
log.Fatalln(err)
}
log.Printf("Received %d file descriptors from systemd.", len(fds))
listenAll(fds)
return
}
namedFDs, err := gosdd.SDListenFDsWithNames(true)
if err != nil {
log.Fatalln(err)
}
log.Printf("Received %d named file descriptors from systemd.", len(namedFDs))
fds := make([]*os.File, 0, len(namedFDs))
for name, fd := range namedFDs {
log.Printf("Adding %q.", name)
fds = append(fds, fd)
}
listenAll(fds)
}
func listenAll(fds []*os.File) {
sig := make(chan os.Signal, 1)
signal.Notify(sig, os.Interrupt, unix.SIGTERM)
srvs := make([]echoServer, 0, len(fds))
wg := &sync.WaitGroup{}
for _, fd := range fds {
ln, err := net.FileListener(fd)
if err != nil {
log.Printf("Failed to make a listener: %s.", err)
continue
}
srv := echoServer{ln, wg}
srvs = append(srvs, srv)
go srv.start()
}
<-sig
for _, srv := range srvs {
srv.stop()
}
wg.Wait()
}
type echoServer struct {
ln net.Listener
wg *sync.WaitGroup
}
func (*echoServer) handle(conn net.Conn) {
defer func() {
if err := conn.Close(); err != nil {
log.Println(err)
}
}()
log.Printf("New connection, local address is %s, remote address is %s.", conn.LocalAddr(), conn.RemoteAddr())
if _, err := fmt.Fprintln(conn, "Hello World!"); err != nil {
log.Println(err)
return
}
r := bufio.NewReader(conn)
for {
s, err := r.ReadString('\n')
if err != nil {
log.Println(err)
return
}
s = strings.Trim(s, "\n ")
log.Printf("Received %q.", s)
if _, err := fmt.Fprintf(conn, "You said %q!\n", s); err != nil {
log.Println(err)
return
}
}
}
func (srv *echoServer) start() {
defer srv.wg.Done()
srv.wg.Add(1)
for {
conn, err := srv.ln.Accept()
if err != nil {
log.Println(err)
return
}
go srv.handle(conn)
}
}
func (srv *echoServer) stop() {
if err := srv.ln.Close(); err != nil {
log.Println(err)
}
}
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