函數rtmp_open()

FFMPEG版本爲3.2 release。

libavformat/rtmpproto.c

 

調用關係:

avformat_open_input(&ic, filename, file_iformat, &o->g->format_opts) ->

init_input(s, filename, &tmp) ->

s->io_open(s, &s->pb, filename, AVIO_FLAG_READ | s->avio_flags, options)，實際回調函數io_open_default() ->

ffio_open_whitelist(pb, url, flags, &s->interrupt_callback, options, s->protocol_whitelist, s->protocol_blacklist); ->

ffurl_open_whitelist(&h, filename, flags, int_cb, options, whitelist, blacklist, NULL);

ffurl_connect(*puc, options) ->

uc->prot->url_open(uc, uc->filename, uc->flags)實際回調函數rtmp_open()

即

Breakpoint 3, rtmp_open (s=0x2768fc0, uri=0x2769018 "rtmp://223.203.1.34:1936/live?vhost=cc.com/stream1_1", flags=1) at libavformat/rtmpproto.c:2608
2608	{
(gdb) bt
#0  rtmp_open (s=0x2768fc0, uri=0x2769018 "rtmp://223.203.1.34:1936/live?vhost=cc.com/stream1_1", flags=1) at libavformat/rtmpproto.c:2608
#1  0x00000000005f35dd in ffurl_connect (uc=0x2768fc0, options=0x7fffffffdaf0) at libavformat/avio.c:210
#2  0x00000000005f3b53 in ffurl_open_whitelist (puc=0x7fffffffda68, filename=<value optimized out>, flags=1, int_cb=<value optimized out>, options=0x7fffffffdaf0, whitelist=0x0, 
    blacklist=0x0, parent=0x0) at libavformat/avio.c:347
#3  0x00000000005f8b55 in ffio_open_whitelist (s=0x2768700, filename=<value optimized out>, flags=<value optimized out>, int_cb=<value optimized out>, options=<value optimized out>, 
    whitelist=<value optimized out>, blacklist=0x0) at libavformat/aviobuf.c:1046
#4  0x00000000006ad1e1 in io_open_default (s=<value optimized out>, pb=<value optimized out>, url=<value optimized out>, flags=<value optimized out>, options=<value optimized out>)
    at libavformat/options.c:112
#5  0x00000000007044bd in init_input (ps=0x7fffffffdbd8, filename=0x7fffffffe758 "rtmp://223.203.1.34:1936/live?vhost=cc.com/stream1_1", fmt=<value optimized out>, options=0x2768428)
    at libavformat/utils.c:415
#6  avformat_open_input (ps=0x7fffffffdbd8, filename=0x7fffffffe758 "rtmp://223.203.1.34:1936/live?vhost=cc.com/stream1_1", fmt=<value optimized out>, options=0x2768428)
    at libavformat/utils.c:529
#7  0x000000000047e65a in open_input_file (o=0x7fffffffdc80, filename=<value optimized out>) at ffmpeg_opt.c:997
#8  0x000000000047bb76 in open_files (l=0x2767998, inout=0x18b68a6 "input", open_file=0x47e220 <open_input_file>) at ffmpeg_opt.c:3135
#9  0x000000000047bde7 in ffmpeg_parse_options (argc=<value optimized out>, argv=<value optimized out>) at ffmpeg_opt.c:3175
#10 0x00000000004927c4 in main (argc=12, argv=0x7fffffffe488) at ffmpeg.c:4564

 

 

Open RTMP connection and verify that the stream can be played.

static int rtmp_open(URLContext *s, const char *uri, int flags)
{
    RTMPContext *rt = s->priv_data;
    char proto[8], hostname[256], path[1024], auth[100], *fname;
    char *old_app, *qmark, *n, fname_buffer[1024];
    uint8_t buf[2048];
    int port;
    AVDictionary *opts = NULL;
    int ret;

    if (rt->listen_timeout > 0)
        rt->listen = 1;

    rt->is_input = !(flags & AVIO_FLAG_WRITE);

    av_url_split(proto, sizeof(proto), auth, sizeof(auth),
                 hostname, sizeof(hostname), &port,
                 path, sizeof(path), s->filename);

    n = strchr(path, ' ');
    if (n) {
        av_log(s, AV_LOG_WARNING,
               "Detected librtmp style URL parameters, these aren't supported "
               "by the libavformat internal RTMP handler currently enabled. "
               "See the documentation for the correct way to pass parameters.\n");
        *n = '\0'; // Trim not supported part
    }

    if (auth[0]) {
        char *ptr = strchr(auth, ':');
        if (ptr) {
            *ptr = '\0';
            av_strlcpy(rt->username, auth, sizeof(rt->username));
            av_strlcpy(rt->password, ptr + 1, sizeof(rt->password));
        }
    }

    if (rt->listen && strcmp(proto, "rtmp")) {
        av_log(s, AV_LOG_ERROR, "rtmp_listen not available for %s\n",
               proto);
        return AVERROR(EINVAL);
    }
    if (!strcmp(proto, "rtmpt") || !strcmp(proto, "rtmpts")) {
        if (!strcmp(proto, "rtmpts"))
            av_dict_set(&opts, "ffrtmphttp_tls", "1", 1);

        /* open the http tunneling connection */
        ff_url_join(buf, sizeof(buf), "ffrtmphttp", NULL, hostname, port, NULL);
    } else if (!strcmp(proto, "rtmps")) {
        /* open the tls connection */
        if (port < 0)
            port = RTMPS_DEFAULT_PORT;
        ff_url_join(buf, sizeof(buf), "tls", NULL, hostname, port, NULL);
    } else if (!strcmp(proto, "rtmpe") || (!strcmp(proto, "rtmpte"))) {
        if (!strcmp(proto, "rtmpte"))
            av_dict_set(&opts, "ffrtmpcrypt_tunneling", "1", 1);

        /* open the encrypted connection */
        ff_url_join(buf, sizeof(buf), "ffrtmpcrypt", NULL, hostname, port, NULL);
        rt->encrypted = 1;
    } else {
        /* open the tcp connection */
        if (port < 0)
            port = RTMP_DEFAULT_PORT;
        if (rt->listen)
            ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port,
                        "?listen&listen_timeout=%d",
                        rt->listen_timeout * 1000);
        else
            ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port, NULL);
    }

reconnect:
    if ((ret = ffurl_open_whitelist(&rt->stream, buf, AVIO_FLAG_READ_WRITE,
                                    &s->interrupt_callback, &opts,
                                    s->protocol_whitelist, s->protocol_blacklist, s)) < 0) {
        av_log(s , AV_LOG_ERROR, "Cannot open connection %s\n", buf);
        goto fail;
    }

    if (rt->swfverify) {
        if ((ret = rtmp_calc_swfhash(s)) < 0)
            goto fail;
    }

    rt->state = STATE_START;
    if (!rt->listen && (ret = rtmp_handshake(s, rt)) < 0)
        goto fail;
    if (rt->listen && (ret = rtmp_server_handshake(s, rt)) < 0)
        goto fail;

    rt->out_chunk_size = 128;
    rt->in_chunk_size  = 128; // Probably overwritten later
    rt->state = STATE_HANDSHAKED;

    // Keep the application name when it has been defined by the user.
    old_app = rt->app;

    rt->app = av_malloc(APP_MAX_LENGTH);
    if (!rt->app) {
        ret = AVERROR(ENOMEM);
        goto fail;
    }

    //extract "app" part from path
    qmark = strchr(path, '?');
    if (qmark && strstr(qmark, "slist=")) {
        char* amp;
        // After slist we have the playpath, the full path is used as app
        av_strlcpy(rt->app, path + 1, APP_MAX_LENGTH);
        fname = strstr(path, "slist=") + 6;
        // Strip any further query parameters from fname
        amp = strchr(fname, '&');
        if (amp) {
            av_strlcpy(fname_buffer, fname, FFMIN(amp - fname + 1,
                                                  sizeof(fname_buffer)));
            fname = fname_buffer;
        }
    } else if (!strncmp(path, "/ondemand/", 10)) {
        fname = path + 10;
        memcpy(rt->app, "ondemand", 9);
    } else {
        char *next = *path ? path + 1 : path;
        char *p = strchr(next, '/');
        if (!p) {
            if (old_app) {
                // If name of application has been defined by the user, assume that
                // playpath is provided in the URL
                fname = next;
            } else {
                fname = NULL;
                av_strlcpy(rt->app, next, APP_MAX_LENGTH);
            }
        } else {
            // make sure we do not mismatch a playpath for an application instance
            char *c = strchr(p + 1, ':');
            fname = strchr(p + 1, '/');
            if (!fname || (c && c < fname)) {
                fname = p + 1;
                av_strlcpy(rt->app, path + 1, FFMIN(p - path, APP_MAX_LENGTH));
            } else {
                fname++;
                av_strlcpy(rt->app, path + 1, FFMIN(fname - path - 1, APP_MAX_LENGTH));
            }
        }
    }

    if (old_app) {
        // The name of application has been defined by the user, override it.
        if (strlen(old_app) >= APP_MAX_LENGTH) {
            ret = AVERROR(EINVAL);
            goto fail;
        }
        av_free(rt->app);
        rt->app = old_app;
    }

    if (!rt->playpath) {
        rt->playpath = av_malloc(PLAYPATH_MAX_LENGTH);
        if (!rt->playpath) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }

        if (fname) {
            int len = strlen(fname);
            if (!strchr(fname, ':') && len >= 4 &&
                (!strcmp(fname + len - 4, ".f4v") ||
                 !strcmp(fname + len - 4, ".mp4"))) {
                memcpy(rt->playpath, "mp4:", 5);
            } else {
                if (len >= 4 && !strcmp(fname + len - 4, ".flv"))
                    fname[len - 4] = '\0';
                rt->playpath[0] = 0;
            }
            av_strlcat(rt->playpath, fname, PLAYPATH_MAX_LENGTH);
        } else {
            rt->playpath[0] = '\0';
        }
    }

    if (!rt->tcurl) {
        rt->tcurl = av_malloc(TCURL_MAX_LENGTH);
        if (!rt->tcurl) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        ff_url_join(rt->tcurl, TCURL_MAX_LENGTH, proto, NULL, hostname,
                    port, "/%s", rt->app);
    }

    if (!rt->flashver) {
        rt->flashver = av_malloc(FLASHVER_MAX_LENGTH);
        if (!rt->flashver) {
            ret = AVERROR(ENOMEM);
            goto fail;
        }
        if (rt->is_input) {
            snprintf(rt->flashver, FLASHVER_MAX_LENGTH, "%s %d,%d,%d,%d",
                    RTMP_CLIENT_PLATFORM, RTMP_CLIENT_VER1, RTMP_CLIENT_VER2,
                    RTMP_CLIENT_VER3, RTMP_CLIENT_VER4);
        } else {
            snprintf(rt->flashver, FLASHVER_MAX_LENGTH,
                    "FMLE/3.0 (compatible; %s)", LIBAVFORMAT_IDENT);
        }
    }

    rt->client_report_size = 1048576;
    rt->bytes_read = 0;
    rt->has_audio = 0;
    rt->has_video = 0;
    rt->received_metadata = 0;
    rt->last_bytes_read = 0;
    rt->server_bw = 2500000;
    rt->duration = 0;

    av_log(s, AV_LOG_DEBUG, "Proto = %s, path = %s, app = %s, fname = %s\n",
           proto, path, rt->app, rt->playpath);
    if (!rt->listen) {
        if ((ret = gen_connect(s, rt)) < 0)
            goto fail;
    } else {
        if ((ret = read_connect(s, s->priv_data)) < 0)
            goto fail;
    }

    do {
        ret = get_packet(s, 1);
    } while (ret == AVERROR(EAGAIN));
    if (ret < 0)
        goto fail;

    if (rt->do_reconnect) {
        int i;
        ffurl_close(rt->stream);
        rt->stream       = NULL;
        rt->do_reconnect = 0;
        rt->nb_invokes   = 0;
        for (i = 0; i < 2; i++)
            memset(rt->prev_pkt[i], 0,
                   sizeof(**rt->prev_pkt) * rt->nb_prev_pkt[i]);
        free_tracked_methods(rt);
        goto reconnect;
    }

    if (rt->is_input) {
        // generate FLV header for demuxer
        rt->flv_size = 13;
        if ((ret = av_reallocp(&rt->flv_data, rt->flv_size)) < 0)
            goto fail;
        rt->flv_off  = 0;
        memcpy(rt->flv_data, "FLV\1\0\0\0\0\011\0\0\0\0", rt->flv_size);

        // Read packets until we reach the first A/V packet or read metadata.
        // If there was a metadata package in front of the A/V packets, we can
        // build the FLV header from this. If we do not receive any metadata,
        // the FLV decoder will allocate the needed streams when their first
        // audio or video packet arrives.
        while (!rt->has_audio && !rt->has_video && !rt->received_metadata) {
            if ((ret = get_packet(s, 0)) < 0)
               goto fail;
        }

        // Either after we have read the metadata or (if there is none) the
        // first packet of an A/V stream, we have a better knowledge about the
        // streams, so set the FLV header accordingly.
        if (rt->has_audio) {
            rt->flv_data[4] |= FLV_HEADER_FLAG_HASAUDIO;
        }
        if (rt->has_video) {
            rt->flv_data[4] |= FLV_HEADER_FLAG_HASVIDEO;
        }

        // If we received the first packet of an A/V stream and no metadata but
        // the server returned a valid duration, create a fake metadata packet
        // to inform the FLV decoder about the duration.
        if (!rt->received_metadata && rt->duration > 0) {
            if ((ret = inject_fake_duration_metadata(rt)) < 0)
                goto fail;
        }
    } else {
        rt->flv_size = 0;
        rt->flv_data = NULL;
        rt->flv_off  = 0;
        rt->skip_bytes = 13;
    }

    s->max_packet_size = rt->stream->max_packet_size;
    s->is_streamed     = 1;
    return 0;

fail:
    av_dict_free(&opts);
    rtmp_close(s);
    return ret;
}

該函數主要包括四個功能：

1.解析url

2.打開鏈接

3. 三次握手

4. Generate 'connect' call and send it to the server

解析url：rtmp://IP:port/app?vhost=name/stream_name

void av_url_split(char *proto, int proto_size,
                  char *authorization, int authorization_size,
                  char *hostname, int hostname_size,
                  int *port_ptr, char *path, int path_size, const char *url)
{
    const char *p, *ls, *ls2, *at, *at2, *col, *brk;

    if (port_ptr)
        *port_ptr = -1;
    if (proto_size > 0)
        proto[0] = 0;
    if (authorization_size > 0)
        authorization[0] = 0;
    if (hostname_size > 0)
        hostname[0] = 0;
    if (path_size > 0)
        path[0] = 0;

    /* parse protocol */
    if ((p = strchr(url, ':'))) {
        av_strlcpy(proto, url, FFMIN(proto_size, p + 1 - url));
        p++; /* skip ':' */
        if (*p == '/')
            p++;
        if (*p == '/')
            p++;
    } else {
        /* no protocol means plain filename */
        av_strlcpy(path, url, path_size);
        return;
    }

    /* separate path from hostname */
    ls = strchr(p, '/');
    ls2 = strchr(p, '?');
    if (!ls)
        ls = ls2;
    else if (ls && ls2)
        ls = FFMIN(ls, ls2);
    if (ls)
        av_strlcpy(path, ls, path_size);
    else
        ls = &p[strlen(p)];  // XXX

    /* the rest is hostname, use that to parse auth/port */
    if (ls != p) {
        /* authorization (user[:pass]@hostname) */
        at2 = p;
        while ((at = strchr(p, '@')) && at < ls) {
            av_strlcpy(authorization, at2,
                       FFMIN(authorization_size, at + 1 - at2));
            p = at + 1; /* skip '@' */
        }

        if (*p == '[' && (brk = strchr(p, ']')) && brk < ls) {
            /* [host]:port */
            av_strlcpy(hostname, p + 1,
                       FFMIN(hostname_size, brk - p));
            if (brk[1] == ':' && port_ptr)
                *port_ptr = atoi(brk + 2);
        } else if ((col = strchr(p, ':')) && col < ls) {
            av_strlcpy(hostname, p,
                       FFMIN(col + 1 - p, hostname_size));
            if (port_ptr)
                *port_ptr = atoi(col + 1);
        } else
            av_strlcpy(hostname, p,
                       FFMIN(ls + 1 - p, hostname_size));
    }
}

根據輸入url獲取hostname，端口號，路徑參數。

打開tcp鏈接

int ff_url_join(char *str, int size, const char *proto,
                const char *authorization, const char *hostname,
                int port, const char *fmt, ...)
{
#if CONFIG_NETWORK
    struct addrinfo hints = { 0 }, *ai;
#endif

    str[0] = '\0';
    if (proto)
        av_strlcatf(str, size, "%s://", proto);
    if (authorization && authorization[0])
        av_strlcatf(str, size, "%s@", authorization);
#if CONFIG_NETWORK && defined(AF_INET6)
    /* Determine if hostname is a numerical IPv6 address,
     * properly escape it within [] in that case. */
    hints.ai_flags = AI_NUMERICHOST;
    if (!getaddrinfo(hostname, NULL, &hints, &ai)) {
        if (ai->ai_family == AF_INET6) {
            av_strlcat(str, "[", size);
            av_strlcat(str, hostname, size);
            av_strlcat(str, "]", size);
        } else {
            av_strlcat(str, hostname, size);
        }
        freeaddrinfo(ai);
    } else
#endif
        /* Not an IPv6 address, just output the plain string. */
        av_strlcat(str, hostname, size);

    if (port >= 0)
        av_strlcatf(str, size, ":%d", port);
    if (fmt) {
        va_list vl;
        size_t len = strlen(str);

        va_start(vl, fmt);
        vsnprintf(str + len, size > len ? size - len : 0, fmt, vl);
        va_end(vl);
    }
    return strlen(str);
}

例如，輸入url爲 rtmp://IP:1936/live?vhost=cc.com/stream_1，

則調用函數ff_url_join(buf, sizeof(buf), "tcp", NULL, hostname, port, NULL);由於rtmp是基於tcp協議。因此buf的內容爲 "tcp://IP:1936"

 

打開URL，即調用tcp協議

int ffurl_open_whitelist(URLContext **puc, const char *filename, int flags,
                         const AVIOInterruptCB *int_cb, AVDictionary **options,
                         const char *whitelist, const char* blacklist,
                         URLContext *parent)
{
    AVDictionary *tmp_opts = NULL;
    AVDictionaryEntry *e;
    int ret = ffurl_alloc(puc, filename, flags, int_cb);
    if (ret < 0)
        return ret;
    if (parent)
        av_opt_copy(*puc, parent);
    if (options &&
        (ret = av_opt_set_dict(*puc, options)) < 0)
        goto fail;
    if (options && (*puc)->prot->priv_data_class &&
        (ret = av_opt_set_dict((*puc)->priv_data, options)) < 0)
        goto fail;

    if (!options)
        options = &tmp_opts;

    av_assert0(!whitelist ||
               !(e=av_dict_get(*options, "protocol_whitelist", NULL, 0)) ||
               !strcmp(whitelist, e->value));
    av_assert0(!blacklist ||
               !(e=av_dict_get(*options, "protocol_blacklist", NULL, 0)) ||
               !strcmp(blacklist, e->value));

    if ((ret = av_dict_set(options, "protocol_whitelist", whitelist, 0)) < 0)
        goto fail;

    if ((ret = av_dict_set(options, "protocol_blacklist", blacklist, 0)) < 0)
        goto fail;

    if ((ret = av_opt_set_dict(*puc, options)) < 0)
        goto fail;

    ret = ffurl_connect(*puc, options);

    if (!ret)
        return 0;
fail:
    ffurl_close(*puc);
    *puc = NULL;
    return ret;
}

即函數uc->prot->url_open(uc, uc->filename, uc->flags)回調tcp_open()

 

函數tcp_open()

/* return non zero if error */
static int tcp_open(URLContext *h, const char *uri, int flags)
{
    struct addrinfo hints = { 0 }, *ai, *cur_ai;
    int port, fd = -1;
    TCPContext *s = h->priv_data;
    const char *p;
    char buf[256];
    int ret;
    char hostname[1024],proto[1024],path[1024];
    char portstr[10];
    s->open_timeout = 5000000;

    av_url_split(proto, sizeof(proto), NULL, 0, hostname, sizeof(hostname),
        &port, path, sizeof(path), uri);
    if (strcmp(proto, "tcp"))
        return AVERROR(EINVAL);
    if (port <= 0 || port >= 65536) {
        av_log(h, AV_LOG_ERROR, "Port missing in uri\n");
        return AVERROR(EINVAL);
    }
    p = strchr(uri, '?');
    if (p) {
        if (av_find_info_tag(buf, sizeof(buf), "listen", p)) {
            char *endptr = NULL;
            s->listen = strtol(buf, &endptr, 10);
            /* assume if no digits were found it is a request to enable it */
            if (buf == endptr)
                s->listen = 1;
        }
        if (av_find_info_tag(buf, sizeof(buf), "timeout", p)) {
            s->rw_timeout = strtol(buf, NULL, 10);
        }
        if (av_find_info_tag(buf, sizeof(buf), "listen_timeout", p)) {
            s->listen_timeout = strtol(buf, NULL, 10);
        }
    }
    if (s->rw_timeout >= 0) {
        s->open_timeout =
        h->rw_timeout   = s->rw_timeout;
    }
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    snprintf(portstr, sizeof(portstr), "%d", port);
    if (s->listen)
        hints.ai_flags |= AI_PASSIVE;
    if (!hostname[0])
        ret = getaddrinfo(NULL, portstr, &hints, &ai);
    else
        ret = getaddrinfo(hostname, portstr, &hints, &ai);
    if (ret) {
        av_log(h, AV_LOG_ERROR,
               "Failed to resolve hostname %s: %s\n",
               hostname, gai_strerror(ret));
        return AVERROR(EIO);
    }

    cur_ai = ai;

 restart:
    fd = ff_socket(cur_ai->ai_family,
                   cur_ai->ai_socktype,
                   cur_ai->ai_protocol);
    if (fd < 0) {
        ret = ff_neterrno();
        goto fail;
    }

    if (s->listen == 2) {
        // multi-client
        if ((ret = ff_listen(fd, cur_ai->ai_addr, cur_ai->ai_addrlen)) < 0)
            goto fail1;
    } else if (s->listen == 1) {
        // single client
        if ((ret = ff_listen_bind(fd, cur_ai->ai_addr, cur_ai->ai_addrlen,
                                  s->listen_timeout, h)) < 0)
            goto fail1;
        // Socket descriptor already closed here. Safe to overwrite to client one.
        fd = ret;
    } else {
        if ((ret = ff_listen_connect(fd, cur_ai->ai_addr, cur_ai->ai_addrlen,
                                     s->open_timeout / 1000, h, !!cur_ai->ai_next)) < 0) {

            if (ret == AVERROR_EXIT)
                goto fail1;
            else
                goto fail;
        }
    }

    h->is_streamed = 1;
    s->fd = fd;
    /* Set the socket's send or receive buffer sizes, if specified.
       If unspecified or setting fails, system default is used. */
    if (s->recv_buffer_size > 0) {
        setsockopt (fd, SOL_SOCKET, SO_RCVBUF, &s->recv_buffer_size, sizeof (s->recv_buffer_size));
    }
    if (s->send_buffer_size > 0) {
        setsockopt (fd, SOL_SOCKET, SO_SNDBUF, &s->send_buffer_size, sizeof (s->send_buffer_size));
    }

    freeaddrinfo(ai);
    return 0;

 fail:
    if (cur_ai->ai_next) {
        /* Retry with the next sockaddr */
        cur_ai = cur_ai->ai_next;
        if (fd >= 0)
            closesocket(fd);
        ret = 0;
        goto restart;
    }
 fail1:
    if (fd >= 0)
        closesocket(fd);
    freeaddrinfo(ai);
    return ret;
}

 

握手rtmp_handshake(s, rt)

/**
 * Perform handshake with the server by means of exchanging pseudorandom data
 * signed with HMAC-SHA2 digest.
 *
 * @return 0 if handshake succeeds, negative value otherwise
 */
static int rtmp_handshake(URLContext *s, RTMPContext *rt)
{
    AVLFG rnd;
    uint8_t tosend    [RTMP_HANDSHAKE_PACKET_SIZE+1] = {
        3,                // unencrypted data
        0, 0, 0, 0,       // client uptime
        RTMP_CLIENT_VER1,
        RTMP_CLIENT_VER2,
        RTMP_CLIENT_VER3,
        RTMP_CLIENT_VER4,
    };
    uint8_t clientdata[RTMP_HANDSHAKE_PACKET_SIZE];
    uint8_t serverdata[RTMP_HANDSHAKE_PACKET_SIZE+1];
    int i;
    int server_pos, client_pos;
    uint8_t digest[32], signature[32];
    int ret, type = 0;

    av_log(s, AV_LOG_DEBUG, "Handshaking...\n");

    av_lfg_init(&rnd, 0xDEADC0DE);
    // generate handshake packet - 1536 bytes of pseudorandom data
    for (i = 9; i <= RTMP_HANDSHAKE_PACKET_SIZE; i++)
        tosend[i] = av_lfg_get(&rnd) >> 24;

    if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
        /* When the client wants to use RTMPE, we have to change the command
         * byte to 0x06 which means to use encrypted data and we have to set
         * the flash version to at least 9.0.115.0. */
        tosend[0] = 6;
        tosend[5] = 128;
        tosend[6] = 0;
        tosend[7] = 3;
        tosend[8] = 2;

        /* Initialize the Diffie-Hellmann context and generate the public key
         * to send to the server. */
        if ((ret = ff_rtmpe_gen_pub_key(rt->stream, tosend + 1)) < 0)
            return ret;
    }

    client_pos = rtmp_handshake_imprint_with_digest(tosend + 1, rt->encrypted);
    if (client_pos < 0)
        return client_pos;

    if ((ret = ffurl_write(rt->stream, tosend,
                           RTMP_HANDSHAKE_PACKET_SIZE + 1)) < 0) {
        av_log(s, AV_LOG_ERROR, "Cannot write RTMP handshake request\n");
        return ret;
    }

    if ((ret = ffurl_read_complete(rt->stream, serverdata,
                                   RTMP_HANDSHAKE_PACKET_SIZE + 1)) < 0) {
        av_log(s, AV_LOG_ERROR, "Cannot read RTMP handshake response\n");
        return ret;
    }

    if ((ret = ffurl_read_complete(rt->stream, clientdata,
                                   RTMP_HANDSHAKE_PACKET_SIZE)) < 0) {
        av_log(s, AV_LOG_ERROR, "Cannot read RTMP handshake response\n");
        return ret;
    }

    av_log(s, AV_LOG_DEBUG, "Type answer %d\n", serverdata[0]);
    av_log(s, AV_LOG_DEBUG, "Server version %d.%d.%d.%d\n",
           serverdata[5], serverdata[6], serverdata[7], serverdata[8]);

    if (rt->is_input && serverdata[5] >= 3) {
        server_pos = rtmp_validate_digest(serverdata + 1, 772);
        if (server_pos < 0)
            return server_pos;

        if (!server_pos) {
            type = 1;
            server_pos = rtmp_validate_digest(serverdata + 1, 8);
            if (server_pos < 0)
                return server_pos;

            if (!server_pos) {
                av_log(s, AV_LOG_ERROR, "Server response validating failed\n");
                return AVERROR(EIO);
            }
        }

        /* Generate SWFVerification token (SHA256 HMAC hash of decompressed SWF,
         * key are the last 32 bytes of the server handshake. */
        if (rt->swfsize) {
            if ((ret = rtmp_calc_swf_verification(s, rt, serverdata + 1 +
                                                  RTMP_HANDSHAKE_PACKET_SIZE - 32)) < 0)
                return ret;
        }

        ret = ff_rtmp_calc_digest(tosend + 1 + client_pos, 32, 0,
                                  rtmp_server_key, sizeof(rtmp_server_key),
                                  digest);
        if (ret < 0)
            return ret;

        ret = ff_rtmp_calc_digest(clientdata, RTMP_HANDSHAKE_PACKET_SIZE - 32,
                                  0, digest, 32, signature);
        if (ret < 0)
            return ret;

        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
            /* Compute the shared secret key sent by the server and initialize
             * the RC4 encryption. */
            if ((ret = ff_rtmpe_compute_secret_key(rt->stream, serverdata + 1,
                                                   tosend + 1, type)) < 0)
                return ret;

            /* Encrypt the signature received by the server. */
            ff_rtmpe_encrypt_sig(rt->stream, signature, digest, serverdata[0]);
        }

        if (memcmp(signature, clientdata + RTMP_HANDSHAKE_PACKET_SIZE - 32, 32)) {
            av_log(s, AV_LOG_ERROR, "Signature mismatch\n");
            return AVERROR(EIO);
        }

        for (i = 0; i < RTMP_HANDSHAKE_PACKET_SIZE; i++)
            tosend[i] = av_lfg_get(&rnd) >> 24;
        ret = ff_rtmp_calc_digest(serverdata + 1 + server_pos, 32, 0,
                                  rtmp_player_key, sizeof(rtmp_player_key),
                                  digest);
        if (ret < 0)
            return ret;

        ret = ff_rtmp_calc_digest(tosend, RTMP_HANDSHAKE_PACKET_SIZE - 32, 0,
                                  digest, 32,
                                  tosend + RTMP_HANDSHAKE_PACKET_SIZE - 32);
        if (ret < 0)
            return ret;

        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
            /* Encrypt the signature to be send to the server. */
            ff_rtmpe_encrypt_sig(rt->stream, tosend +
                                 RTMP_HANDSHAKE_PACKET_SIZE - 32, digest,
                                 serverdata[0]);
        }

        // write reply back to the server
        if ((ret = ffurl_write(rt->stream, tosend,
                               RTMP_HANDSHAKE_PACKET_SIZE)) < 0)
            return ret;

        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
            /* Set RC4 keys for encryption and update the keystreams. */
            if ((ret = ff_rtmpe_update_keystream(rt->stream)) < 0)
                return ret;
        }
    } else {
        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
            /* Compute the shared secret key sent by the server and initialize
             * the RC4 encryption. */
            if ((ret = ff_rtmpe_compute_secret_key(rt->stream, serverdata + 1,
                            tosend + 1, 1)) < 0)
                return ret;

            if (serverdata[0] == 9) {
                /* Encrypt the signature received by the server. */
                ff_rtmpe_encrypt_sig(rt->stream, signature, digest,
                                     serverdata[0]);
            }
        }

        if ((ret = ffurl_write(rt->stream, serverdata + 1,
                               RTMP_HANDSHAKE_PACKET_SIZE)) < 0)
            return ret;

        if (CONFIG_FFRTMPCRYPT_PROTOCOL && rt->encrypted) {
            /* Set RC4 keys for encryption and update the keystreams. */
            if ((ret = ff_rtmpe_update_keystream(rt->stream)) < 0)
                return ret;
        }
    }

    return 0;
}

其中：

(ret = ffurl_write(rt->stream, tosend,
                           RTMP_HANDSHAKE_PACKET_SIZE + 1))發送C0和C1到服務器，共1537個字節。寫操做調用函數tcp_write()。

(ret = ffurl_read_complete(rt->stream, serverdata,
                                   RTMP_HANDSHAKE_PACKET_SIZE + 1))接受服務器的響應S0和S1的數據，共1537個字節。讀操做調用函數tcp_read()。

(ret = ffurl_read_complete(rt->stream, clientdata,
                                   RTMP_HANDSHAKE_PACKET_SIZE))接受服務器的響應S2的數據，共1536個字節。讀操做調用函數tcp_read()。

(ret = ffurl_write(rt->stream, serverdata + 1,
                               RTMP_HANDSHAKE_PACKET_SIZE))發送C2(內容爲S1)到服務器，共1536個字節。寫操做調用函數tcp_write()。

Generate 'connect' call and send it to the server.

/**
 * Generate 'connect' call and send it to the server.
 */
static int gen_connect(URLContext *s, RTMPContext *rt)
{
    RTMPPacket pkt;
    uint8_t *p;
    int ret;

    if ((ret = ff_rtmp_packet_create(&pkt, RTMP_SYSTEM_CHANNEL, RTMP_PT_INVOKE,
                                     0, 4096 + APP_MAX_LENGTH)) < 0)
        return ret;

    p = pkt.data;

    ff_amf_write_string(&p, "connect");
    ff_amf_write_number(&p, ++rt->nb_invokes);
    ff_amf_write_object_start(&p);
    ff_amf_write_field_name(&p, "app");
    ff_amf_write_string2(&p, rt->app, rt->auth_params);

    if (!rt->is_input) {
        ff_amf_write_field_name(&p, "type");
        ff_amf_write_string(&p, "nonprivate");
    }
    ff_amf_write_field_name(&p, "flashVer");
    ff_amf_write_string(&p, rt->flashver);

    if (rt->swfurl) {
        ff_amf_write_field_name(&p, "swfUrl");
        ff_amf_write_string(&p, rt->swfurl);
    }

    ff_amf_write_field_name(&p, "tcUrl");
    ff_amf_write_string2(&p, rt->tcurl, rt->auth_params);
    if (rt->is_input) {
        ff_amf_write_field_name(&p, "fpad");
        ff_amf_write_bool(&p, 0);
        ff_amf_write_field_name(&p, "capabilities");
        ff_amf_write_number(&p, 15.0);

        /* Tell the server we support all the audio codecs except
         * SUPPORT_SND_INTEL (0x0008) and SUPPORT_SND_UNUSED (0x0010)
         * which are unused in the RTMP protocol implementation. */
        ff_amf_write_field_name(&p, "audioCodecs");
        ff_amf_write_number(&p, 4071.0);
        ff_amf_write_field_name(&p, "videoCodecs");
        ff_amf_write_number(&p, 252.0);
        ff_amf_write_field_name(&p, "videoFunction");
        ff_amf_write_number(&p, 1.0);

        if (rt->pageurl) {
            ff_amf_write_field_name(&p, "pageUrl");
            ff_amf_write_string(&p, rt->pageurl);
        }
    }
    ff_amf_write_object_end(&p);

    if (rt->conn) {
        char *param = rt->conn;

        // Write arbitrary AMF data to the Connect message.
        while (param) {
            char *sep;
            param += strspn(param, " ");
            if (!*param)
                break;
            sep = strchr(param, ' ');
            if (sep)
                *sep = '\0';
            if ((ret = rtmp_write_amf_data(s, param, &p)) < 0) {
                // Invalid AMF parameter.
                ff_rtmp_packet_destroy(&pkt);
                return ret;
            }

            if (sep)
                param = sep + 1;
            else
                break;
        }
    }

    pkt.size = p - pkt.data;

    return rtmp_send_packet(rt, &pkt, 1);
}