2 * MMS protocol over TCP
3 * Copyright (c) 2006,2007 Ryan Martell
4 * Copyright (c) 2007 Björn Axelsson
5 * Copyright (c) 2010 Zhentan Feng <spyfeng at gmail dot com>
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
25 * MMS protocol specification:
26 * [1]http://msdn.microsoft.com/en-us/library/cc234711(PROT.10).aspx
27 * ASF specification. Revision 01.20.03.
28 * [2]http://msdn.microsoft.com/en-us/library/bb643323.aspx
33 #include "libavutil/intreadwrite.h"
34 #include "libavcodec/bytestream.h"
38 #define LOCAL_ADDRESS 0xc0a80081 // FIXME get and use correct local ip address.
39 #define LOCAL_PORT 1037 // as above.
40 /** Client to server packet types. */
42 CS_PKT_INITIAL = 0x01,
43 CS_PKT_PROTOCOL_SELECT = 0x02,
44 CS_PKT_MEDIA_FILE_REQUEST = 0x05,
45 CS_PKT_START_FROM_PKT_ID = 0x07,
46 CS_PKT_STREAM_PAUSE = 0x09,
47 CS_PKT_STREAM_CLOSE = 0x0d,
48 CS_PKT_MEDIA_HEADER_REQUEST = 0x15,
49 CS_PKT_TIMING_DATA_REQUEST = 0x18,
50 CS_PKT_USER_PASSWORD = 0x1a,
51 CS_PKT_KEEPALIVE = 0x1b,
52 CS_PKT_STREAM_ID_REQUEST = 0x33,
55 /** Server to client packet types. */
57 /** Control packets. */
59 SC_PKT_CLIENT_ACCEPTED = 0x01,
60 SC_PKT_PROTOCOL_ACCEPTED = 0x02,
61 SC_PKT_PROTOCOL_FAILED = 0x03,
62 SC_PKT_MEDIA_PKT_FOLLOWS = 0x05,
63 SC_PKT_MEDIA_FILE_DETAILS = 0x06,
64 SC_PKT_HEADER_REQUEST_ACCEPTED = 0x11,
65 SC_PKT_TIMING_TEST_REPLY = 0x15,
66 SC_PKT_PASSWORD_REQUIRED = 0x1a,
67 SC_PKT_KEEPALIVE = 0x1b,
68 SC_PKT_STREAM_STOPPED = 0x1e,
69 SC_PKT_STREAM_CHANGING = 0x20,
70 SC_PKT_STREAM_ID_ACCEPTED = 0x21,
73 /** Pseudo packets. */
81 SC_PKT_ASF_HEADER = 0x010000,// make it bigger than 0xFF in case of
82 SC_PKT_ASF_MEDIA = 0x010001,// receiving false data packets.
91 int outgoing_packet_seq; ///< Outgoing packet sequence number.
92 char path[256]; ///< Path of the resource being asked for.
93 char host[128]; ///< Host of the resources.
95 URLContext *mms_hd; ///< TCP connection handle
96 MMSStream streams[MAX_STREAMS];
98 /** Buffer for outgoing packets. */
100 uint8_t *write_out_ptr; ///< Pointer for writting the buffer.
101 uint8_t out_buffer[512]; ///< Buffer for outgoing packet.
104 /** Buffer for incoming packets. */
106 uint8_t in_buffer[8192]; ///< Buffer for incoming packets.
107 uint8_t *read_in_ptr; ///< Pointer for reading from incoming buffer.
108 int remaining_in_len; ///< Reading length from incoming buffer.
111 int incoming_packet_seq; ///< Incoming packet sequence number.
112 int incoming_flags; ///< Incoming packet flags.
114 int packet_id; ///< Identifier for packets in the current stream.
115 unsigned int header_packet_id; ///< default is 2.
117 /** Internal handling of the ASF header */
119 uint8_t *asf_header; ///< Stored ASF header.
120 int asf_header_size; ///< Size of stored ASF header.
121 int header_parsed; ///< The header has been received and parsed.
123 int asf_header_read_size;
126 int stream_num; ///< stream numbers.
130 /** Create MMST command packet header */
131 static void start_command_packet(MMSContext *mms, MMSCSPacketType packet_type)
133 mms->write_out_ptr = mms->out_buffer;
135 bytestream_put_le32(&mms->write_out_ptr, 1); // start sequence
136 bytestream_put_le32(&mms->write_out_ptr, 0xb00bface);
137 bytestream_put_le32(&mms->write_out_ptr, 0); // Length starts from after the protocol type bytes
138 bytestream_put_le32(&mms->write_out_ptr, MKTAG('M','M','S',' '));
139 bytestream_put_le32(&mms->write_out_ptr, 0);
140 bytestream_put_le32(&mms->write_out_ptr, mms->outgoing_packet_seq++);
141 bytestream_put_le64(&mms->write_out_ptr, 0); // timestamp
142 bytestream_put_le32(&mms->write_out_ptr, 0);
143 bytestream_put_le16(&mms->write_out_ptr, packet_type);
144 bytestream_put_le16(&mms->write_out_ptr, 3); // direction to server
147 /** Add prefixes to MMST command packet. */
148 static void insert_command_prefixes(MMSContext *mms,
149 uint32_t prefix1, uint32_t prefix2)
151 bytestream_put_le32(&mms->write_out_ptr, prefix1); // first prefix
152 bytestream_put_le32(&mms->write_out_ptr, prefix2); // second prefix
155 /** Send a prepared MMST command packet. */
156 static int send_command_packet(MMSContext *mms)
158 int len= mms->write_out_ptr - mms->out_buffer;
159 int exact_length = (len + 7) & ~7;
160 int first_length= exact_length - 16;
161 int len8= first_length/8;
164 // update packet length fields.
165 AV_WL32(mms->out_buffer + 8, first_length);
166 AV_WL32(mms->out_buffer + 16, len8);
167 AV_WL32(mms->out_buffer + 32, len8-2);
168 memset(mms->write_out_ptr, 0, exact_length - len);
171 write_result= url_write(mms->mms_hd, mms->out_buffer, exact_length);
172 if(write_result != exact_length) {
173 dprintf(NULL, "url_write returned: %d != %d\n",
174 write_result, exact_length);
181 static void mms_put_utf16(MMSContext *mms, uint8_t *src)
184 int size = mms->write_out_ptr - mms->out_buffer;
186 init_put_byte(&bic, mms->write_out_ptr,
187 sizeof(mms->out_buffer) - size, 1, NULL, NULL, NULL, NULL);
189 len = ff_put_str16_nolen(&bic, src);
190 mms->write_out_ptr += len;
193 static int send_time_test_data(MMSContext *mms)
195 start_command_packet(mms, CS_PKT_TIMING_DATA_REQUEST);
196 insert_command_prefixes(mms, 0xf0f0f0f1, 0x0004000b);
197 return send_command_packet(mms);
200 static int send_protocol_select(MMSContext *mms)
202 char data_string[256];
204 start_command_packet(mms, CS_PKT_PROTOCOL_SELECT);
205 insert_command_prefixes(mms, 0, 0xffffffff);
206 bytestream_put_le32(&mms->write_out_ptr, 0); // maxFunnelBytes
207 bytestream_put_le32(&mms->write_out_ptr, 0x00989680); // maxbitRate
208 bytestream_put_le32(&mms->write_out_ptr, 2); // funnelMode
209 snprintf(data_string, sizeof(data_string), "\\\\%d.%d.%d.%d\\%s\\%d",
210 (LOCAL_ADDRESS>>24)&0xff,
211 (LOCAL_ADDRESS>>16)&0xff,
212 (LOCAL_ADDRESS>>8)&0xff,
217 mms_put_utf16(mms, data_string);
218 return send_command_packet(mms);
221 static int send_media_file_request(MMSContext *mms)
223 start_command_packet(mms, CS_PKT_MEDIA_FILE_REQUEST);
224 insert_command_prefixes(mms, 1, 0xffffffff);
225 bytestream_put_le32(&mms->write_out_ptr, 0);
226 bytestream_put_le32(&mms->write_out_ptr, 0);
227 mms_put_utf16(mms, mms->path + 1); // +1 for skip "/"
229 return send_command_packet(mms);
232 static void handle_packet_stream_changing_type(MMSContext *mms)
234 dprintf(NULL, "Stream changing!\n");
236 // 40 is the packet header size, 7 is the prefix size.
237 mms->header_packet_id= AV_RL32(mms->in_buffer + 40 + 7);
238 dprintf(NULL, "Changed header prefix to 0x%x", mms->header_packet_id);
241 static int send_keepalive_packet(MMSContext *mms)
243 // respond to a keepalive with a keepalive...
244 start_command_packet(mms, CS_PKT_KEEPALIVE);
245 insert_command_prefixes(mms, 1, 0x100FFFF);
246 return send_command_packet(mms);
249 /** Pad media packets smaller than max_packet_size and/or adjust read position
251 static void pad_media_packet(MMSContext *mms)
253 if(mms->remaining_in_len<mms->asf_packet_len) {
254 int padding_size = mms->asf_packet_len - mms->remaining_in_len;
255 memset(mms->in_buffer + mms->remaining_in_len, 0, padding_size);
256 mms->remaining_in_len += padding_size;
260 /** Read incoming MMST media, header or command packet. */
261 static MMSSCPacketType get_tcp_server_response(MMSContext *mms)
264 MMSSCPacketType packet_type= -1;
267 if((read_result= url_read_complete(mms->mms_hd, mms->in_buffer, 8))==8) {
268 // handle command packet.
269 if(AV_RL32(mms->in_buffer + 4)==0xb00bface) {
270 mms->incoming_flags= mms->in_buffer[3];
271 read_result= url_read_complete(mms->mms_hd, mms->in_buffer+8, 4);
272 if(read_result == 4) {
273 int length_remaining= AV_RL32(mms->in_buffer+8) + 4;
276 dprintf(NULL, "Length remaining is %d\n", length_remaining);
277 // read the rest of the packet.
278 if (length_remaining < 0
279 || length_remaining > sizeof(mms->in_buffer) - 12) {
280 dprintf(NULL, "Incoming message len %d exceeds buffer len %d\n",
281 length_remaining, sizeof(mms->in_buffer) - 12);
284 read_result = url_read_complete(mms->mms_hd, mms->in_buffer + 12,
286 if (read_result == length_remaining) {
287 packet_type= AV_RL16(mms->in_buffer+36);
289 dprintf(NULL, "read for packet type failed%d!\n", read_result);
292 hr = AV_RL32(mms->in_buffer + 40);
294 dprintf(NULL, "The server side send back error code:0x%x\n", hr);
298 dprintf(NULL, "read for length remaining failed%d!\n", read_result);
302 int length_remaining;
306 // note we cache the first 8 bytes,
307 // then fill up the buffer with the others
308 tmp = AV_RL16(mms->in_buffer + 6);
309 length_remaining = (tmp - 8) & 0xffff;
310 mms->incoming_packet_seq = AV_RL32(mms->in_buffer);
311 packet_id_type = mms->in_buffer[4];
312 mms->incoming_flags = mms->in_buffer[5];
314 if (length_remaining < 0
315 || length_remaining > sizeof(mms->in_buffer) - 8) {
316 dprintf(NULL, "Incoming data len %d exceeds buffer len %d\n",
317 length_remaining, sizeof(mms->in_buffer));
320 mms->remaining_in_len = length_remaining;
321 mms->read_in_ptr = mms->in_buffer;
322 read_result= url_read_complete(mms->mms_hd, mms->in_buffer, length_remaining);
323 if(read_result != length_remaining) {
324 dprintf(NULL, "read_bytes result: %d asking for %d\n",
325 read_result, length_remaining);
328 // if we successfully read everything.
329 if(packet_id_type == mms->header_packet_id) {
330 packet_type = SC_PKT_ASF_HEADER;
331 // Store the asf header
332 if(!mms->header_parsed) {
333 void *p = av_realloc(mms->asf_header,
335 + mms->remaining_in_len);
337 av_freep(&mms->asf_header);
338 return AVERROR(ENOMEM);
341 memcpy(mms->asf_header + mms->asf_header_size,
343 mms->remaining_in_len);
344 mms->asf_header_size += mms->remaining_in_len;
346 // 0x04 means asf header is sent in multiple packets.
347 if (mms->incoming_flags == 0x04)
349 } else if(packet_id_type == mms->packet_id) {
350 packet_type = SC_PKT_ASF_MEDIA;
352 dprintf(NULL, "packet id type %d is old.", packet_id_type);
358 // preprocess some packet type
359 if(packet_type == SC_PKT_KEEPALIVE) {
360 send_keepalive_packet(mms);
362 } else if(packet_type == SC_PKT_STREAM_CHANGING) {
363 handle_packet_stream_changing_type(mms);
364 } else if(packet_type == SC_PKT_ASF_MEDIA) {
365 pad_media_packet(mms);
370 dprintf(NULL, "Read error (or cancelled) returned %d!\n", read_result);
371 packet_type = SC_PKT_CANCEL;
373 dprintf(NULL, "Read result of zero?!\n");
374 packet_type = SC_PKT_NO_DATA;
381 static int mms_safe_send_recv(MMSContext *mms,
382 int (*send_fun)(MMSContext *mms),
383 const MMSSCPacketType expect_type)
385 MMSSCPacketType type;
387 int ret = send_fun(mms);
389 dprintf(NULL, "Send Packet error before expecting recv packet %d\n", expect_type);
394 if ((type = get_tcp_server_response(mms)) != expect_type) {
395 dprintf(NULL,"Unexpected packet type %d with type %d\n", type, expect_type);
402 static int send_media_header_request(MMSContext *mms)
404 start_command_packet(mms, CS_PKT_MEDIA_HEADER_REQUEST);
405 insert_command_prefixes(mms, 1, 0);
406 bytestream_put_le32(&mms->write_out_ptr, 0);
407 bytestream_put_le32(&mms->write_out_ptr, 0x00800000);
408 bytestream_put_le32(&mms->write_out_ptr, 0xffffffff);
409 bytestream_put_le32(&mms->write_out_ptr, 0);
410 bytestream_put_le32(&mms->write_out_ptr, 0);
411 bytestream_put_le32(&mms->write_out_ptr, 0);
413 // the media preroll value in milliseconds?
414 bytestream_put_le32(&mms->write_out_ptr, 0);
415 bytestream_put_le32(&mms->write_out_ptr, 0x40AC2000);
416 bytestream_put_le32(&mms->write_out_ptr, 2);
417 bytestream_put_le32(&mms->write_out_ptr, 0);
419 return send_command_packet(mms);
422 /** Send the initial handshake. */
423 static int send_startup_packet(MMSContext *mms)
425 char data_string[256];
426 // SubscriberName is defined in MS specification linked below.
427 // The guid value can be any valid value.
428 // http://download.microsoft.com/
429 // download/9/5/E/95EF66AF-9026-4BB0-A41D-A4F81802D92C/%5BMS-WMSP%5D.pdf
430 snprintf(data_string, sizeof(data_string),
431 "NSPlayer/7.0.0.1956; {%s}; Host: %s",
432 "7E667F5D-A661-495E-A512-F55686DDA178", mms->host);
434 start_command_packet(mms, CS_PKT_INITIAL);
435 insert_command_prefixes(mms, 0, 0x0004000b);
436 bytestream_put_le32(&mms->write_out_ptr, 0x0003001c);
437 mms_put_utf16(mms, data_string);
438 return send_command_packet(mms);
441 static int asf_header_parser(MMSContext *mms)
443 uint8_t *p = mms->asf_header;
445 int flags, stream_id;
448 if (mms->asf_header_size < sizeof(ff_asf_guid) * 2 + 22 ||
449 memcmp(p, ff_asf_header, sizeof(ff_asf_guid)))
452 end = mms->asf_header + mms->asf_header_size;
454 p += sizeof(ff_asf_guid) + 14;
455 while(end - p >= sizeof(ff_asf_guid) + 8) {
456 uint64_t chunksize = AV_RL64(p + sizeof(ff_asf_guid));
457 if (!chunksize || chunksize > end - p) {
458 dprintf(NULL, "chunksize is exceptional value:%"PRId64"!\n", chunksize);
461 if (!memcmp(p, ff_asf_file_header, sizeof(ff_asf_guid))) {
462 /* read packet size */
463 if (end - p > sizeof(ff_asf_guid) * 2 + 68) {
464 mms->asf_packet_len = AV_RL32(p + sizeof(ff_asf_guid) * 2 + 64);
465 if (mms->asf_packet_len <= 0 || mms->asf_packet_len > sizeof(mms->in_buffer)) {
466 dprintf(NULL,"Too large packet len:%d"
467 " may overwrite in_buffer when padding", mms->asf_packet_len);
471 } else if (!memcmp(p, ff_asf_stream_header, sizeof(ff_asf_guid))) {
472 flags = AV_RL16(p + sizeof(ff_asf_guid)*3 + 24);
473 stream_id = flags & 0x7F;
474 //The second condition is for checking CS_PKT_STREAM_ID_REQUEST packet size,
475 //we can calcuate the packet size by stream_num.
476 //Please see function send_stream_selection_request().
477 if (mms->stream_num < MAX_STREAMS &&
478 46 + mms->stream_num * 6 < sizeof(mms->out_buffer)) {
479 mms->streams[mms->stream_num].id = stream_id;
482 dprintf(NULL, "Too many streams.\n");
485 } else if (!memcmp(p, ff_asf_head1_guid, sizeof(ff_asf_guid))) {
486 chunksize = 46; // see references [2] section 3.4. This should be set 46.
494 /** Send MMST stream selection command based on the AVStream->discard values. */
495 static int send_stream_selection_request(MMSContext *mms)
499 // send the streams we want back...
500 start_command_packet(mms, CS_PKT_STREAM_ID_REQUEST);
501 bytestream_put_le32(&mms->write_out_ptr, mms->stream_num); // stream nums
502 for(i= 0; i<mms->stream_num; i++) {
503 bytestream_put_le16(&mms->write_out_ptr, 0xffff); // flags
504 bytestream_put_le16(&mms->write_out_ptr, mms->streams[i].id); // stream id
505 bytestream_put_le16(&mms->write_out_ptr, 0); // selection
507 return send_command_packet(mms);
510 static int read_data(MMSContext *mms, uint8_t *buf, const int buf_size)
513 read_size = FFMIN(buf_size, mms->remaining_in_len);
514 memcpy(buf, mms->read_in_ptr, read_size);
515 mms->remaining_in_len -= read_size;
516 mms->read_in_ptr += read_size;
520 /** Read at most one media packet (or a whole header). */
521 static int read_mms_packet(MMSContext *mms, uint8_t *buf, int buf_size)
527 if(mms->asf_header_read_size < mms->asf_header_size && !mms->is_playing) {
528 /* Read from ASF header buffer */
529 size_to_copy= FFMIN(buf_size,
530 mms->asf_header_size - mms->asf_header_read_size);
531 memcpy(buf, mms->asf_header + mms->asf_header_read_size, size_to_copy);
532 mms->asf_header_read_size += size_to_copy;
533 result += size_to_copy;
534 dprintf(NULL, "Copied %d bytes from stored header. left: %d\n",
535 size_to_copy, mms->asf_header_size - mms->asf_header_read_size);
536 if (mms->asf_header_size == mms->asf_header_read_size) {
537 av_freep(&mms->asf_header);
540 } else if(mms->remaining_in_len) {
541 /* Read remaining packet data to buffer.
542 * the result can not be zero because remaining_in_len is positive.*/
543 result = read_data(mms, buf, buf_size);
545 /* Read from network */
546 int err = mms_safe_send_recv(mms, NULL, SC_PKT_ASF_MEDIA);
548 if(mms->remaining_in_len>mms->asf_packet_len) {
549 dprintf(NULL, "Incoming packet"
550 "larger than the asf packet size stated (%d>%d)\n",
551 mms->remaining_in_len, mms->asf_packet_len);
554 // copy the data to the packet buffer.
555 result = read_data(mms, buf, buf_size);
557 dprintf(NULL, "read asf media paket size is zero!\n");
562 dprintf(NULL, "read packet error!\n");
566 } while(!result); // only return one packet.
570 static int send_close_packet(MMSContext *mms)
572 start_command_packet(mms, CS_PKT_STREAM_CLOSE);
573 insert_command_prefixes(mms, 1, 1);
575 return send_command_packet(mms);
578 /** Close the MMSH/MMST connection */
579 static int mms_close(URLContext *h)
581 MMSContext *mms = (MMSContext *)h->priv_data;
584 send_close_packet(mms);
585 url_close(mms->mms_hd);
588 /* free all separately allocated pointers in mms */
589 av_free(mms->asf_header);
590 av_freep(&h->priv_data);
595 static int mms_open(URLContext *h, const char *uri, int flags)
602 mms = h->priv_data = av_mallocz(sizeof(MMSContext));
604 return AVERROR(ENOMEM);
606 // only for MMS over TCP, so set proto = NULL
607 av_url_split(NULL, 0, NULL, 0,
608 mms->host, sizeof(mms->host), &port, mms->path,
609 sizeof(mms->path), uri);
612 port = 1755; // defaut mms protocol port
614 // establish tcp connection.
615 ff_url_join(tcpname, sizeof(tcpname), "tcp", NULL, mms->host, port, NULL);
616 err = url_open(&mms->mms_hd, tcpname, URL_RDWR);
620 mms->packet_id = 3; // default, initial value.
621 mms->header_packet_id = 2; // default, initial value.
622 err = mms_safe_send_recv(mms, send_startup_packet, SC_PKT_CLIENT_ACCEPTED);
625 err = mms_safe_send_recv(mms, send_time_test_data, SC_PKT_TIMING_TEST_REPLY);
628 err = mms_safe_send_recv(mms, send_protocol_select, SC_PKT_PROTOCOL_ACCEPTED);
631 err = mms_safe_send_recv(mms, send_media_file_request, SC_PKT_MEDIA_FILE_DETAILS);
634 err = mms_safe_send_recv(mms, send_media_header_request, SC_PKT_HEADER_REQUEST_ACCEPTED);
637 err = mms_safe_send_recv(mms, NULL, SC_PKT_ASF_HEADER);
640 if((mms->incoming_flags != 0X08) && (mms->incoming_flags != 0X0C))
642 err = asf_header_parser(mms);
644 dprintf(NULL, "asf header parsed failed!\n");
647 mms->header_parsed = 1;
649 if (!mms->asf_packet_len || !mms->stream_num)
652 dprintf(NULL, "Leaving open (success)\n");
656 dprintf(NULL, "Leaving open (failure: %d)\n", err);
660 static int send_media_packet_request(MMSContext *mms)
662 start_command_packet(mms, CS_PKT_START_FROM_PKT_ID);
663 insert_command_prefixes(mms, 1, 0x0001FFFF);
664 bytestream_put_le64(&mms->write_out_ptr, 0); // seek timestamp
665 bytestream_put_le32(&mms->write_out_ptr, 0xffffffff); // unknown
666 bytestream_put_le32(&mms->write_out_ptr, 0xffffffff); // packet offset
667 bytestream_put_byte(&mms->write_out_ptr, 0xff); // max stream time limit
668 bytestream_put_byte(&mms->write_out_ptr, 0xff); // max stream time limit
669 bytestream_put_byte(&mms->write_out_ptr, 0xff); // max stream time limit
670 bytestream_put_byte(&mms->write_out_ptr, 0x00); // stream time limit flag
672 mms->packet_id++; // new packet_id
673 bytestream_put_le32(&mms->write_out_ptr, mms->packet_id);
674 return send_command_packet(mms);
678 static void clear_stream_buffers(MMSContext *mms)
680 mms->remaining_in_len = 0;
681 mms->read_in_ptr = mms->in_buffer;
684 /** Read ASF data through the protocol. */
685 static int mms_read(URLContext *h, uint8_t *buf, int size)
687 /* TODO: see tcp.c:tcp_read() about a possible timeout scheme */
688 MMSContext *mms = h->priv_data;
691 /* Since we read the header at open(), this shouldn't be possible */
692 assert(mms->header_parsed);
694 if (!mms->is_playing) {
695 dprintf(NULL, "mms_read() before play().\n");
696 clear_stream_buffers(mms);
697 result = mms_safe_send_recv(mms, send_stream_selection_request, SC_PKT_STREAM_ID_ACCEPTED);
700 // send media packet request
701 result = mms_safe_send_recv(mms, send_media_packet_request, SC_PKT_MEDIA_PKT_FOLLOWS);
706 return read_mms_packet(mms, buf, size);
709 URLProtocol mmst_protocol = {