Material do artigo retirado do meu canal zen .
Usando o TShark para analisar pacotes RTP
No último artigo, montamos um circuito de controle remoto a partir de um gerador e um detector de sinais tonais, cuja comunicação foi realizada usando um fluxo RTP.
RTP-. RTP- .
, RTP, , mstest6.c , , , mstest_common.c, include:
#include <mediastreamer2/msfilter.h>
#include <mediastreamer2/msticker.h>
#include <mediastreamer2/msrtp.h>
#include <ortp/rtpsession.h>
#include <ortp/payloadtype.h>
define PCMU 0
void register_payloads(void)
{
rtp_profile_set_payload (&av_profile, PCMU, &payload_type_pcm8000);
}
static RtpSession *create_rtpsession (int loc_rtp_port, int loc_rtcp_port, bool_t ipv6, RtpSessionMode mode)
{
RtpSession *rtpr; rtpr = rtp_session_new ((int) mode);
rtp_session_set_scheduling_mode (rtpr, 0);
rtp_session_set_blocking_mode (rtpr, 0);
rtp_session_enable_adaptive_jitter_compensation (rtpr, TRUE);
rtp_session_set_symmetric_rtp (rtpr, TRUE);
rtp_session_set_local_addr (rtpr, ipv6 ? "::" : "0.0.0.0", loc_rtp_port, loc_rtcp_port);
rtp_session_signal_connect (rtpr, "timestamp_jump", (RtpCallback) rtp_session_resync, 0);
rtp_session_signal_connect (rtpr, "ssrc_changed", (RtpCallback) rtp_session_resync, 0);
rtp_session_set_ssrc_changed_threshold (rtpr, 0);
rtp_session_set_send_payload_type(rtpr, PCMU);
rtp_session_enable_rtcp (rtpr, FALSE);
return rtpr;
}
:
#include <mediastreamer2/dtmfgen.h>
#include <mediastreamer2/msrtp.h>
#include "mstest_common.c"
int main()
{
ms_init();
MSFilter *voidsource = ms_filter_new(MS_VOID_SOURCE_ID);
MSFilter *dtmfgen = ms_filter_new(MS_DTMF_GEN_ID);
MSFilter *encoder = ms_filter_create_encoder("PCMU");
register_payloads();
RtpSession *tx_rtp_session = create_rtpsession (8010, 8011, FALSE, RTP_SESSION_SENDONLY);
rtp_session_set_remote_addr_and_port(tx_rtp_session,"127.0.0.1", 7010, 7011);
rtp_session_set_send_payload_type(tx_rtp_session, PCMU);
MSFilter *rtpsend = ms_filter_new(MS_RTP_SEND_ID);
ms_filter_call_method(rtpsend, MS_RTP_SEND_SET_SESSION, tx_rtp_session);
MSTicker *ticker_tx = ms_ticker_new();
ms_filter_link(voidsource, 0, dtmfgen, 0);
ms_filter_link(dtmfgen, 0, encoder, 0);
ms_filter_link(encoder, 0, rtpsend, 0);
ms_ticker_attach(ticker_tx, voidsource);
MSDtmfGenCustomTone dtmf_cfg;
dtmf_cfg.tone_name[0] = 0;
dtmf_cfg.duration = 1000;
dtmf_cfg.frequencies[0] = 440;
dtmf_cfg.frequencies[1] = 0;
dtmf_cfg.amplitude = 1.0;
dtmf_cfg.interval = 0.;
dtmf_cfg.repeat_count = 0.;
char key='9';
printf(" , .\n"
" 0.\n");
while(key != '0')
{
key = getchar();
if ((key >= 49) && (key <= 54))
{
printf(" : %c\n", key);
dtmf_cfg.frequencies[0] = 440 + 100*(key-49);
ms_filter_call_method(dtmfgen, MS_DTMF_GEN_PLAY_CUSTOM, (void*)&dtmf_cfg);
}
ms_usleep(20000);
}
}
, :
include <mediastreamer2/mssndcard.h>
include <mediastreamer2/mstonedetector.h>
include <mediastreamer2/msrtp.h>
include <mediastreamer2/mseventqueue.h>
include "mstest_common.c"
static void tone_detected_cb(void *data, MSFilter *f, unsigned int event_id,MSToneDetectorEvent *ev)
{
printf(" : %s\n", ev->tone_name);
}
int main()
{
ms_init();
MSSndCard *card_playback = ms_snd_card_manager_get_default_card(ms_snd_card_manager_get());
MSFilter *snd_card_write = ms_snd_card_create_writer(card_playback);
MSFilter *detector = ms_filter_new(MS_TONE_DETECTOR_ID);
ms_filter_call_method(detector, MS_TONE_DETECTOR_CLEAR_SCANS, 0);
ms_filter_set_notify_callback(detector, (MSFilterNotifyFunc)tone_detected_cb, NULL);
MSToneDetectorDef scan[6]=
{
{"V+",440, 100, 0.1},
{"V-",540, 100, 0.1},
{"C+",640, 100, 0.1},
{"C-",740, 100, 0.1},
{"ON",840, 100, 0.1},
{"OFF", 940, 100, 0.1}
};
int i;
for (i = 0; i < 6; i++)
{
ms_filter_call_method(detector, MS_TONE_DETECTOR_ADD_SCAN, &scan[i]);
}
MSFilter *decoder=ms_filter_create_decoder("PCMU");
register_payloads();
MSFilter *rtprecv = ms_filter_new(MS_RTP_RECV_ID);
RtpSession *rx_rtp_session = create_rtpsession (7010, 7011, FALSE, RTP_SESSION_RECVONLY);
ms_filter_call_method(rtprecv, MS_RTP_RECV_SET_SESSION, rx_rtp_session);
MSTicker *ticker_rx = ms_ticker_new();
ms_filter_link(rtprecv, 0, decoder, 0);
ms_filter_link(decoder, 0, detector, 0);
ms_filter_link(detector, 0, snd_card_write, 0);
ms_ticker_attach(ticker_rx, rtprecv);
char key='9';
printf( " 0.\n");
while(key != '0')
{
key = getchar();
ms_usleep(20000);
}
}
, , . — 1 6 , . . , — RTP- .
, Wireshrk — TShark. TShark , . Wireshark , Wireshark.
Wireshark, . TShark, VoIP , .
TShark :
sudo apt-get install tshark
, :
tshark --version
.
, tshark . loopback ( ), TShark -i lo:
sudo tshark -i lo
(, , ). , , . , , . Ctrl-C (8010): -f "udp port 8010". :
sudo tshark -i lo -f "udp port 8010"
( 10 ):
1 0.000000000 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
2 0.020059705 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
3 0.040044409 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
4 0.060057104 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
5 0.080082311 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
6 0.100597153 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
7 0.120122668 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
8 0.140204789 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
9 0.160719008 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
10 0.180673685 127.0.0.1 → 127.0.0.1 UDP 214 8010 → 7010 Len=172
, , , . , , . :
.
.
IP- IP- .
, UDP, RTP- UDP-.
.
.
, , RTP- 172 , , , UDP- 214 .
UDP-, TShark :
sudo tshark -i lo -f "udp port 8010" -P -V -O rtp -o rtp.heuristic_rtp:TRUE -x
Como resultado, a saída do programa será enriquecida - uma descriptografia do conteúdo interno do pacote que o causou será adicionada a cada evento. Para visualizar melhor os dados de saída, você pode parar o TShark pressionando Ctrl-C ou duplicar sua saída em um arquivo, adicionando um pipeline ao programa tee com o nome do arquivo, tee <filename> no comando start:
sudo tshark -i lo -f "udp port 8010" -P -V -O rtp -o rtp.heuristic_rtp:TRUE -x | tee log.txt
Agora, vamos ver o que conseguimos no arquivo, aqui está o primeiro pacote:
1 0.000000000 127.0.0.1 → 127.0.0.1 RTP 214 PT=ITU-T G.711 PCMU, SSRC=0x6B8B4567, Seq=58366, Time=355368720
Frame 1: 214 bytes on wire (1712 bits), 214 bytes captured (1712 bits) on interface 0
Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst: 00:00:00_00:00:00 (00:00:00:00:00:00)
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1User Datagram Protocol, Src Port: 8010, Dst Port: 7010
Real-Time Transport Protocol [Stream setup by HEUR RT (frame 1)]
[Setup frame: 1]
[Setup Method: HEUR RT]
10.. .... = Version: RFC 1889 Version (2)
..0. .... = Padding: False
...0 .... = Extension: False
.... 0000 = Contributing source identifiers count: 0
0... .... = Marker: False
Payload type: ITU-T G.711 PCMU (0)
Sequence number: 58366 [Extended sequence number: 58366]
Timestamp: 355368720
Synchronization Source identifier: 0x6b8b4567 (1804289383)
Payload: ffffffffffffffffffffffffffffffffffffffffffffffff...
0000 00 00 00 00 00 00 00 00 00 00 00 00 08 00 45 00 ..............E.
0010 00 c8 3c 69 40 00 40 11 ff b9 7f 00 00 01 7f 00 ..<i@.@.........
0020 00 01 1f 4a 1b 62 00 b4 fe c7 80 00 e3 fe 15 2e ...J.b..........
0030 7f 10 6b 8b 45 67 ff ff ff ff ff ff ff ff ff ff ..k.Eg..........
0040 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0050 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0060 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0070 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0080 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
0090 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00a0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00b0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00c0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
00d0 ff ff ff ff ff ff ......
Vamos dedicar o seguinte artigo à análise das informações contidas nesta lista e, inevitavelmente, falaremos sobre a estrutura interna do pacote RTP.