1// Copyright 2012 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package net
6
7import (
8	"fmt"
9	"internal/testenv"
10	"io"
11	"os"
12	"reflect"
13	"runtime"
14	"sync"
15	"testing"
16	"time"
17)
18
19func BenchmarkTCP4OneShot(b *testing.B) {
20	benchmarkTCP(b, false, false, "127.0.0.1:0")
21}
22
23func BenchmarkTCP4OneShotTimeout(b *testing.B) {
24	benchmarkTCP(b, false, true, "127.0.0.1:0")
25}
26
27func BenchmarkTCP4Persistent(b *testing.B) {
28	benchmarkTCP(b, true, false, "127.0.0.1:0")
29}
30
31func BenchmarkTCP4PersistentTimeout(b *testing.B) {
32	benchmarkTCP(b, true, true, "127.0.0.1:0")
33}
34
35func BenchmarkTCP6OneShot(b *testing.B) {
36	if !supportsIPv6() {
37		b.Skip("ipv6 is not supported")
38	}
39	benchmarkTCP(b, false, false, "[::1]:0")
40}
41
42func BenchmarkTCP6OneShotTimeout(b *testing.B) {
43	if !supportsIPv6() {
44		b.Skip("ipv6 is not supported")
45	}
46	benchmarkTCP(b, false, true, "[::1]:0")
47}
48
49func BenchmarkTCP6Persistent(b *testing.B) {
50	if !supportsIPv6() {
51		b.Skip("ipv6 is not supported")
52	}
53	benchmarkTCP(b, true, false, "[::1]:0")
54}
55
56func BenchmarkTCP6PersistentTimeout(b *testing.B) {
57	if !supportsIPv6() {
58		b.Skip("ipv6 is not supported")
59	}
60	benchmarkTCP(b, true, true, "[::1]:0")
61}
62
63func benchmarkTCP(b *testing.B, persistent, timeout bool, laddr string) {
64	testHookUninstaller.Do(uninstallTestHooks)
65
66	const msgLen = 512
67	conns := b.N
68	numConcurrent := runtime.GOMAXPROCS(-1) * 2
69	msgs := 1
70	if persistent {
71		conns = numConcurrent
72		msgs = b.N / conns
73		if msgs == 0 {
74			msgs = 1
75		}
76		if conns > b.N {
77			conns = b.N
78		}
79	}
80	sendMsg := func(c Conn, buf []byte) bool {
81		n, err := c.Write(buf)
82		if n != len(buf) || err != nil {
83			b.Log(err)
84			return false
85		}
86		return true
87	}
88	recvMsg := func(c Conn, buf []byte) bool {
89		for read := 0; read != len(buf); {
90			n, err := c.Read(buf)
91			read += n
92			if err != nil {
93				b.Log(err)
94				return false
95			}
96		}
97		return true
98	}
99	ln, err := Listen("tcp", laddr)
100	if err != nil {
101		b.Fatal(err)
102	}
103	defer ln.Close()
104	serverSem := make(chan bool, numConcurrent)
105	// Acceptor.
106	go func() {
107		for {
108			c, err := ln.Accept()
109			if err != nil {
110				break
111			}
112			serverSem <- true
113			// Server connection.
114			go func(c Conn) {
115				defer func() {
116					c.Close()
117					<-serverSem
118				}()
119				if timeout {
120					c.SetDeadline(time.Now().Add(time.Hour)) // Not intended to fire.
121				}
122				var buf [msgLen]byte
123				for m := 0; m < msgs; m++ {
124					if !recvMsg(c, buf[:]) || !sendMsg(c, buf[:]) {
125						break
126					}
127				}
128			}(c)
129		}
130	}()
131	clientSem := make(chan bool, numConcurrent)
132	for i := 0; i < conns; i++ {
133		clientSem <- true
134		// Client connection.
135		go func() {
136			defer func() {
137				<-clientSem
138			}()
139			c, err := Dial("tcp", ln.Addr().String())
140			if err != nil {
141				b.Log(err)
142				return
143			}
144			defer c.Close()
145			if timeout {
146				c.SetDeadline(time.Now().Add(time.Hour)) // Not intended to fire.
147			}
148			var buf [msgLen]byte
149			for m := 0; m < msgs; m++ {
150				if !sendMsg(c, buf[:]) || !recvMsg(c, buf[:]) {
151					break
152				}
153			}
154		}()
155	}
156	for i := 0; i < numConcurrent; i++ {
157		clientSem <- true
158		serverSem <- true
159	}
160}
161
162func BenchmarkTCP4ConcurrentReadWrite(b *testing.B) {
163	benchmarkTCPConcurrentReadWrite(b, "127.0.0.1:0")
164}
165
166func BenchmarkTCP6ConcurrentReadWrite(b *testing.B) {
167	if !supportsIPv6() {
168		b.Skip("ipv6 is not supported")
169	}
170	benchmarkTCPConcurrentReadWrite(b, "[::1]:0")
171}
172
173func benchmarkTCPConcurrentReadWrite(b *testing.B, laddr string) {
174	testHookUninstaller.Do(uninstallTestHooks)
175
176	// The benchmark creates GOMAXPROCS client/server pairs.
177	// Each pair creates 4 goroutines: client reader/writer and server reader/writer.
178	// The benchmark stresses concurrent reading and writing to the same connection.
179	// Such pattern is used in net/http and net/rpc.
180
181	b.StopTimer()
182
183	P := runtime.GOMAXPROCS(0)
184	N := b.N / P
185	W := 1000
186
187	// Setup P client/server connections.
188	clients := make([]Conn, P)
189	servers := make([]Conn, P)
190	ln, err := Listen("tcp", laddr)
191	if err != nil {
192		b.Fatal(err)
193	}
194	defer ln.Close()
195	done := make(chan bool)
196	go func() {
197		for p := 0; p < P; p++ {
198			s, err := ln.Accept()
199			if err != nil {
200				b.Error(err)
201				return
202			}
203			servers[p] = s
204		}
205		done <- true
206	}()
207	for p := 0; p < P; p++ {
208		c, err := Dial("tcp", ln.Addr().String())
209		if err != nil {
210			b.Fatal(err)
211		}
212		clients[p] = c
213	}
214	<-done
215
216	b.StartTimer()
217
218	var wg sync.WaitGroup
219	wg.Add(4 * P)
220	for p := 0; p < P; p++ {
221		// Client writer.
222		go func(c Conn) {
223			defer wg.Done()
224			var buf [1]byte
225			for i := 0; i < N; i++ {
226				v := byte(i)
227				for w := 0; w < W; w++ {
228					v *= v
229				}
230				buf[0] = v
231				_, err := c.Write(buf[:])
232				if err != nil {
233					b.Error(err)
234					return
235				}
236			}
237		}(clients[p])
238
239		// Pipe between server reader and server writer.
240		pipe := make(chan byte, 128)
241
242		// Server reader.
243		go func(s Conn) {
244			defer wg.Done()
245			var buf [1]byte
246			for i := 0; i < N; i++ {
247				_, err := s.Read(buf[:])
248				if err != nil {
249					b.Error(err)
250					return
251				}
252				pipe <- buf[0]
253			}
254		}(servers[p])
255
256		// Server writer.
257		go func(s Conn) {
258			defer wg.Done()
259			var buf [1]byte
260			for i := 0; i < N; i++ {
261				v := <-pipe
262				for w := 0; w < W; w++ {
263					v *= v
264				}
265				buf[0] = v
266				_, err := s.Write(buf[:])
267				if err != nil {
268					b.Error(err)
269					return
270				}
271			}
272			s.Close()
273		}(servers[p])
274
275		// Client reader.
276		go func(c Conn) {
277			defer wg.Done()
278			var buf [1]byte
279			for i := 0; i < N; i++ {
280				_, err := c.Read(buf[:])
281				if err != nil {
282					b.Error(err)
283					return
284				}
285			}
286			c.Close()
287		}(clients[p])
288	}
289	wg.Wait()
290}
291
292type resolveTCPAddrTest struct {
293	network       string
294	litAddrOrName string
295	addr          *TCPAddr
296	err           error
297}
298
299var resolveTCPAddrTests = []resolveTCPAddrTest{
300	{"tcp", "127.0.0.1:0", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil},
301	{"tcp4", "127.0.0.1:65535", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 65535}, nil},
302
303	{"tcp", "[::1]:0", &TCPAddr{IP: ParseIP("::1"), Port: 0}, nil},
304	{"tcp6", "[::1]:65535", &TCPAddr{IP: ParseIP("::1"), Port: 65535}, nil},
305
306	{"tcp", "[::1%en0]:1", &TCPAddr{IP: ParseIP("::1"), Port: 1, Zone: "en0"}, nil},
307	{"tcp6", "[::1%911]:2", &TCPAddr{IP: ParseIP("::1"), Port: 2, Zone: "911"}, nil},
308
309	{"", "127.0.0.1:0", &TCPAddr{IP: IPv4(127, 0, 0, 1), Port: 0}, nil}, // Go 1.0 behavior
310	{"", "[::1]:0", &TCPAddr{IP: ParseIP("::1"), Port: 0}, nil},         // Go 1.0 behavior
311
312	{"tcp", ":12345", &TCPAddr{Port: 12345}, nil},
313
314	{"http", "127.0.0.1:0", nil, UnknownNetworkError("http")},
315
316	{"tcp", "127.0.0.1:http", &TCPAddr{IP: ParseIP("127.0.0.1"), Port: 80}, nil},
317	{"tcp", "[::ffff:127.0.0.1]:http", &TCPAddr{IP: ParseIP("::ffff:127.0.0.1"), Port: 80}, nil},
318	{"tcp", "[2001:db8::1]:http", &TCPAddr{IP: ParseIP("2001:db8::1"), Port: 80}, nil},
319	{"tcp4", "127.0.0.1:http", &TCPAddr{IP: ParseIP("127.0.0.1"), Port: 80}, nil},
320	{"tcp4", "[::ffff:127.0.0.1]:http", &TCPAddr{IP: ParseIP("127.0.0.1"), Port: 80}, nil},
321	{"tcp6", "[2001:db8::1]:http", &TCPAddr{IP: ParseIP("2001:db8::1"), Port: 80}, nil},
322
323	{"tcp4", "[2001:db8::1]:http", nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: "2001:db8::1"}},
324	{"tcp6", "127.0.0.1:http", nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: "127.0.0.1"}},
325	{"tcp6", "[::ffff:127.0.0.1]:http", nil, &AddrError{Err: errNoSuitableAddress.Error(), Addr: "::ffff:127.0.0.1"}},
326}
327
328func TestResolveTCPAddr(t *testing.T) {
329	origTestHookLookupIP := testHookLookupIP
330	defer func() { testHookLookupIP = origTestHookLookupIP }()
331	testHookLookupIP = lookupLocalhost
332
333	for _, tt := range resolveTCPAddrTests {
334		addr, err := ResolveTCPAddr(tt.network, tt.litAddrOrName)
335		if !reflect.DeepEqual(addr, tt.addr) || !reflect.DeepEqual(err, tt.err) {
336			t.Errorf("ResolveTCPAddr(%q, %q) = %#v, %v, want %#v, %v", tt.network, tt.litAddrOrName, addr, err, tt.addr, tt.err)
337			continue
338		}
339		if err == nil {
340			addr2, err := ResolveTCPAddr(addr.Network(), addr.String())
341			if !reflect.DeepEqual(addr2, tt.addr) || err != tt.err {
342				t.Errorf("(%q, %q): ResolveTCPAddr(%q, %q) = %#v, %v, want %#v, %v", tt.network, tt.litAddrOrName, addr.Network(), addr.String(), addr2, err, tt.addr, tt.err)
343			}
344		}
345	}
346}
347
348var tcpListenerNameTests = []struct {
349	net   string
350	laddr *TCPAddr
351}{
352	{"tcp4", &TCPAddr{IP: IPv4(127, 0, 0, 1)}},
353	{"tcp4", &TCPAddr{}},
354	{"tcp4", nil},
355}
356
357func TestTCPListenerName(t *testing.T) {
358	testenv.MustHaveExternalNetwork(t)
359
360	for _, tt := range tcpListenerNameTests {
361		ln, err := ListenTCP(tt.net, tt.laddr)
362		if err != nil {
363			t.Fatal(err)
364		}
365		defer ln.Close()
366		la := ln.Addr()
367		if a, ok := la.(*TCPAddr); !ok || a.Port == 0 {
368			t.Fatalf("got %v; expected a proper address with non-zero port number", la)
369		}
370	}
371}
372
373func TestIPv6LinkLocalUnicastTCP(t *testing.T) {
374	testenv.MustHaveExternalNetwork(t)
375
376	if !supportsIPv6() {
377		t.Skip("IPv6 is not supported")
378	}
379
380	for i, tt := range ipv6LinkLocalUnicastTCPTests {
381		ln, err := Listen(tt.network, tt.address)
382		if err != nil {
383			// It might return "LookupHost returned no
384			// suitable address" error on some platforms.
385			t.Log(err)
386			continue
387		}
388		ls, err := (&streamListener{Listener: ln}).newLocalServer()
389		if err != nil {
390			t.Fatal(err)
391		}
392		defer ls.teardown()
393		ch := make(chan error, 1)
394		handler := func(ls *localServer, ln Listener) { transponder(ln, ch) }
395		if err := ls.buildup(handler); err != nil {
396			t.Fatal(err)
397		}
398		if la, ok := ln.Addr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
399			t.Fatalf("got %v; expected a proper address with zone identifier", la)
400		}
401
402		c, err := Dial(tt.network, ls.Listener.Addr().String())
403		if err != nil {
404			t.Fatal(err)
405		}
406		defer c.Close()
407		if la, ok := c.LocalAddr().(*TCPAddr); !ok || !tt.nameLookup && la.Zone == "" {
408			t.Fatalf("got %v; expected a proper address with zone identifier", la)
409		}
410		if ra, ok := c.RemoteAddr().(*TCPAddr); !ok || !tt.nameLookup && ra.Zone == "" {
411			t.Fatalf("got %v; expected a proper address with zone identifier", ra)
412		}
413
414		if _, err := c.Write([]byte("TCP OVER IPV6 LINKLOCAL TEST")); err != nil {
415			t.Fatal(err)
416		}
417		b := make([]byte, 32)
418		if _, err := c.Read(b); err != nil {
419			t.Fatal(err)
420		}
421
422		for err := range ch {
423			t.Errorf("#%d: %v", i, err)
424		}
425	}
426}
427
428func TestTCPConcurrentAccept(t *testing.T) {
429	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
430	ln, err := Listen("tcp", "127.0.0.1:0")
431	if err != nil {
432		t.Fatal(err)
433	}
434	const N = 10
435	var wg sync.WaitGroup
436	wg.Add(N)
437	for i := 0; i < N; i++ {
438		go func() {
439			for {
440				c, err := ln.Accept()
441				if err != nil {
442					break
443				}
444				c.Close()
445			}
446			wg.Done()
447		}()
448	}
449	attempts := 10 * N
450	fails := 0
451	d := &Dialer{Timeout: 200 * time.Millisecond}
452	for i := 0; i < attempts; i++ {
453		c, err := d.Dial("tcp", ln.Addr().String())
454		if err != nil {
455			fails++
456		} else {
457			c.Close()
458		}
459	}
460	ln.Close()
461	wg.Wait()
462	if fails > attempts/9 { // see issues 7400 and 7541
463		t.Fatalf("too many Dial failed: %v", fails)
464	}
465	if fails > 0 {
466		t.Logf("# of failed Dials: %v", fails)
467	}
468}
469
470func TestTCPReadWriteAllocs(t *testing.T) {
471	if runtime.Compiler == "gccgo" {
472		t.Skip("skipping for gccgo until escape analysis is enabled")
473	}
474
475	switch runtime.GOOS {
476	case "plan9":
477		// The implementation of asynchronous cancelable
478		// I/O on Plan 9 allocates memory.
479		// See net/fd_io_plan9.go.
480		t.Skipf("not supported on %s", runtime.GOOS)
481	case "nacl":
482		// NaCl needs to allocate pseudo file descriptor
483		// stuff. See syscall/fd_nacl.go.
484		t.Skipf("not supported on %s", runtime.GOOS)
485	}
486
487	ln, err := Listen("tcp", "127.0.0.1:0")
488	if err != nil {
489		t.Fatal(err)
490	}
491	defer ln.Close()
492	var server Conn
493	errc := make(chan error, 1)
494	go func() {
495		var err error
496		server, err = ln.Accept()
497		errc <- err
498	}()
499	client, err := Dial("tcp", ln.Addr().String())
500	if err != nil {
501		t.Fatal(err)
502	}
503	defer client.Close()
504	if err := <-errc; err != nil {
505		t.Fatal(err)
506	}
507	defer server.Close()
508
509	var buf [128]byte
510	allocs := testing.AllocsPerRun(1000, func() {
511		_, err := server.Write(buf[:])
512		if err != nil {
513			t.Fatal(err)
514		}
515		_, err = io.ReadFull(client, buf[:])
516		if err != nil {
517			t.Fatal(err)
518		}
519	})
520	// For gccgo changed "> 0" to "> 7".
521	if allocs > 7 {
522		t.Fatalf("got %v; want 0", allocs)
523	}
524
525	var bufwrt [128]byte
526	ch := make(chan bool)
527	defer close(ch)
528	go func() {
529		for <-ch {
530			_, err := server.Write(bufwrt[:])
531			errc <- err
532		}
533	}()
534	allocs = testing.AllocsPerRun(1000, func() {
535		ch <- true
536		if _, err = io.ReadFull(client, buf[:]); err != nil {
537			t.Fatal(err)
538		}
539		if err := <-errc; err != nil {
540			t.Fatal(err)
541		}
542	})
543	if allocs > 0 {
544		t.Fatalf("got %v; want 0", allocs)
545	}
546}
547
548func TestTCPStress(t *testing.T) {
549	const conns = 2
550	const msgLen = 512
551	msgs := int(1e4)
552	if testing.Short() {
553		msgs = 1e2
554	}
555
556	sendMsg := func(c Conn, buf []byte) bool {
557		n, err := c.Write(buf)
558		if n != len(buf) || err != nil {
559			t.Log(err)
560			return false
561		}
562		return true
563	}
564	recvMsg := func(c Conn, buf []byte) bool {
565		for read := 0; read != len(buf); {
566			n, err := c.Read(buf)
567			read += n
568			if err != nil {
569				t.Log(err)
570				return false
571			}
572		}
573		return true
574	}
575
576	ln, err := Listen("tcp", "127.0.0.1:0")
577	if err != nil {
578		t.Fatal(err)
579	}
580	done := make(chan bool)
581	// Acceptor.
582	go func() {
583		defer func() {
584			done <- true
585		}()
586		for {
587			c, err := ln.Accept()
588			if err != nil {
589				break
590			}
591			// Server connection.
592			go func(c Conn) {
593				defer c.Close()
594				var buf [msgLen]byte
595				for m := 0; m < msgs; m++ {
596					if !recvMsg(c, buf[:]) || !sendMsg(c, buf[:]) {
597						break
598					}
599				}
600			}(c)
601		}
602	}()
603	for i := 0; i < conns; i++ {
604		// Client connection.
605		go func() {
606			defer func() {
607				done <- true
608			}()
609			c, err := Dial("tcp", ln.Addr().String())
610			if err != nil {
611				t.Log(err)
612				return
613			}
614			defer c.Close()
615			var buf [msgLen]byte
616			for m := 0; m < msgs; m++ {
617				if !sendMsg(c, buf[:]) || !recvMsg(c, buf[:]) {
618					break
619				}
620			}
621		}()
622	}
623	for i := 0; i < conns; i++ {
624		<-done
625	}
626	ln.Close()
627	<-done
628}
629
630func TestTCPSelfConnect(t *testing.T) {
631	if runtime.GOOS == "windows" {
632		// TODO(brainman): do not know why it hangs.
633		t.Skip("known-broken test on windows")
634	}
635
636	ln, err := newLocalListener("tcp")
637	if err != nil {
638		t.Fatal(err)
639	}
640	var d Dialer
641	c, err := d.Dial(ln.Addr().Network(), ln.Addr().String())
642	if err != nil {
643		ln.Close()
644		t.Fatal(err)
645	}
646	network := c.LocalAddr().Network()
647	laddr := *c.LocalAddr().(*TCPAddr)
648	c.Close()
649	ln.Close()
650
651	// Try to connect to that address repeatedly.
652	n := 100000
653	if testing.Short() {
654		n = 1000
655	}
656	switch runtime.GOOS {
657	case "darwin", "dragonfly", "freebsd", "netbsd", "openbsd", "plan9", "solaris", "windows":
658		// Non-Linux systems take a long time to figure
659		// out that there is nothing listening on localhost.
660		n = 100
661	}
662	for i := 0; i < n; i++ {
663		d.Timeout = time.Millisecond
664		c, err := d.Dial(network, laddr.String())
665		if err == nil {
666			addr := c.LocalAddr().(*TCPAddr)
667			if addr.Port == laddr.Port || addr.IP.Equal(laddr.IP) {
668				t.Errorf("Dial %v should fail", addr)
669			} else {
670				t.Logf("Dial %v succeeded - possibly racing with other listener", addr)
671			}
672			c.Close()
673		}
674	}
675}
676
677// Test that >32-bit reads work on 64-bit systems.
678// On 32-bit systems this tests that maxint reads work.
679func TestTCPBig(t *testing.T) {
680	if !*testTCPBig {
681		t.Skip("test disabled; use -tcpbig to enable")
682	}
683
684	for _, writev := range []bool{false, true} {
685		t.Run(fmt.Sprintf("writev=%v", writev), func(t *testing.T) {
686			ln, err := newLocalListener("tcp")
687			if err != nil {
688				t.Fatal(err)
689			}
690			defer ln.Close()
691
692			x := int(1 << 30)
693			x = x*5 + 1<<20 // just over 5 GB on 64-bit, just over 1GB on 32-bit
694			done := make(chan int)
695			go func() {
696				defer close(done)
697				c, err := ln.Accept()
698				if err != nil {
699					t.Error(err)
700					return
701				}
702				buf := make([]byte, x)
703				var n int
704				if writev {
705					var n64 int64
706					n64, err = (&Buffers{buf}).WriteTo(c)
707					n = int(n64)
708				} else {
709					n, err = c.Write(buf)
710				}
711				if n != len(buf) || err != nil {
712					t.Errorf("Write(buf) = %d, %v, want %d, nil", n, err, x)
713				}
714				c.Close()
715			}()
716
717			c, err := Dial("tcp", ln.Addr().String())
718			if err != nil {
719				t.Fatal(err)
720			}
721			buf := make([]byte, x)
722			n, err := io.ReadFull(c, buf)
723			if n != len(buf) || err != nil {
724				t.Errorf("Read(buf) = %d, %v, want %d, nil", n, err, x)
725			}
726			c.Close()
727			<-done
728		})
729	}
730}
731
732func TestCopyPipeIntoTCP(t *testing.T) {
733	ln, err := newLocalListener("tcp")
734	if err != nil {
735		t.Fatal(err)
736	}
737	defer ln.Close()
738
739	errc := make(chan error, 1)
740	defer func() {
741		if err := <-errc; err != nil {
742			t.Error(err)
743		}
744	}()
745	go func() {
746		c, err := ln.Accept()
747		if err != nil {
748			errc <- err
749			return
750		}
751		defer c.Close()
752
753		buf := make([]byte, 100)
754		n, err := io.ReadFull(c, buf)
755		if err != io.ErrUnexpectedEOF || n != 2 {
756			errc <- fmt.Errorf("got err=%q n=%v; want err=%q n=2", err, n, io.ErrUnexpectedEOF)
757			return
758		}
759
760		errc <- nil
761	}()
762
763	c, err := Dial("tcp", ln.Addr().String())
764	if err != nil {
765		t.Fatal(err)
766	}
767	defer c.Close()
768
769	r, w, err := os.Pipe()
770	if err != nil {
771		t.Fatal(err)
772	}
773	defer r.Close()
774
775	errc2 := make(chan error, 1)
776	defer func() {
777		if err := <-errc2; err != nil {
778			t.Error(err)
779		}
780	}()
781
782	defer w.Close()
783
784	go func() {
785		_, err := io.Copy(c, r)
786		errc2 <- err
787	}()
788
789	// Split write into 2 packets. That makes Windows TransmitFile
790	// drop second packet.
791	packet := make([]byte, 1)
792	_, err = w.Write(packet)
793	if err != nil {
794		t.Fatal(err)
795	}
796	time.Sleep(100 * time.Millisecond)
797	_, err = w.Write(packet)
798	if err != nil {
799		t.Fatal(err)
800	}
801}
802