Merge branch 'simple_http_server_api_implementation' of http://git.klaxa.eu/git/ffmpeg

Reviewed-by: Nicolas George <george@nsup.org>
Merged-by: Michael Niedermayer <michael@niedermayer.cc>

doc/examples/Makefile

@@ -18,6 +18,7 @@ EXAMPLES=       avio_list_dir                      \
                 extract_mvs                        \
                 filtering_video                    \
                 filtering_audio                    \
+                http_multiclient                   \
                 metadata                           \
                 muxing                             \
                 remuxing                           \

doc/examples/http_multiclient.c

+/*
+ * Copyright (c) 2015 Stephan Holljes
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * @file
+ * libavformat multi-client network API usage example.
+ *
+ * @example http_multiclient.c
+ * This example will serve a file without decoding or demuxing it over http.
+ * Multiple clients can connect and will receive the same file.
+ */
+
+#include <libavformat/avformat.h>
+#include <libavutil/opt.h>
+#include <unistd.h>
+
+void process_client(AVIOContext *client, const char *in_uri)
+{
+    AVIOContext *input = NULL;
+    uint8_t buf[1024];
+    int ret, n, reply_code;
+    char *resource = NULL;
+    while ((ret = avio_handshake(client)) > 0) {
+        av_opt_get(client, "resource", AV_OPT_SEARCH_CHILDREN, &resource);
+        // check for strlen(resource) is necessary, because av_opt_get()
+        // may return empty string.
+        if (resource && strlen(resource))
+            break;
+    }
+    if (ret < 0)
+        goto end;
+    av_log(client, AV_LOG_TRACE, "resource=%p\n", resource);
+    if (resource && resource[0] == '/' && !strcmp((resource + 1), in_uri)) {
+        reply_code = 200;
+    } else {
+        reply_code = AVERROR_HTTP_NOT_FOUND;
+    }
+    if ((ret = av_opt_set_int(client, "reply_code", reply_code, AV_OPT_SEARCH_CHILDREN)) < 0) {
+        av_log(client, AV_LOG_ERROR, "Failed to set reply_code: %s.\n", av_err2str(ret));
+        goto end;
+    }
+    av_log(client, AV_LOG_TRACE, "Set reply code to %d\n", reply_code);
+
+    while ((ret = avio_handshake(client)) > 0);
+
+    if (ret < 0)
+        goto end;
+
+    fprintf(stderr, "Handshake performed.\n");
+    if (reply_code != 200)
+        goto end;
+    fprintf(stderr, "Opening input file.\n");
+    if ((ret = avio_open2(&input, in_uri, AVIO_FLAG_READ, NULL, NULL)) < 0) {
+        av_log(input, AV_LOG_ERROR, "Failed to open input: %s: %s.\n", in_uri,
+               av_err2str(ret));
+        goto end;
+    }
+    for(;;) {
+        n = avio_read(input, buf, sizeof(buf));
+        if (n < 0) {
+            if (n == AVERROR_EOF)
+                break;
+            av_log(input, AV_LOG_ERROR, "Error reading from input: %s.\n",
+                   av_err2str(n));
+            break;
+        }
+        avio_write(client, buf, n);
+        avio_flush(client);
+    }
+end:
+    fprintf(stderr, "Flushing client\n");
+    avio_flush(client);
+    fprintf(stderr, "Closing client\n");
+    avio_close(client);
+    fprintf(stderr, "Closing input\n");
+    avio_close(input);
+}
+
+int main(int argc, char **argv)
+{
+    av_log_set_level(AV_LOG_TRACE);
+    AVDictionary *options = NULL;
+    AVIOContext *client = NULL, *server = NULL;
+    const char *in_uri, *out_uri;
+    int ret, pid;
+    if (argc < 3) {
+        printf("usage: %s input http://hostname[:port]\n"
+               "API example program to serve http to multiple clients.\n"
+               "\n", argv[0]);
+        return 1;
+    }
+
+    in_uri = argv[1];
+    out_uri = argv[2];
+
+    av_register_all();
+    avformat_network_init();
+
+    if ((ret = av_dict_set(&options, "listen", "2", 0)) < 0) {
+        fprintf(stderr, "Failed to set listen mode for server: %s\n", av_err2str(ret));
+        return ret;
+    }
+    if ((ret = avio_open2(&server, out_uri, AVIO_FLAG_WRITE, NULL, &options)) < 0) {
+        fprintf(stderr, "Failed to open server: %s\n", av_err2str(ret));
+        return ret;
+    }
+    fprintf(stderr, "Entering main loop.\n");
+    for(;;) {
+        if ((ret = avio_accept(server, &client)) < 0)
+            goto end;
+        fprintf(stderr, "Accepted client, forking process.\n");
+        // XXX: Since we don't reap our children and don't ignore signals
+        //      this produces zombie processes.
+        pid = fork();
+        if (pid < 0) {
+            perror("Fork failed");
+            ret = AVERROR(errno);
+            goto end;
+        }
+        if (pid == 0) {
+            fprintf(stderr, "In child.\n");
+            process_client(client, in_uri);
+            avio_close(server);
+            exit(0);
+        }
+        if (pid > 0)
+            avio_close(client);
+    }
+end:
+    avio_close(server);
+    if (ret < 0 && ret != AVERROR_EOF) {
+        fprintf(stderr, "Some errors occured: %s\n", av_err2str(ret));
+        return 1;
+    }
+    return 0;
+}

doc/protocols.texi

@@ -304,6 +304,8 @@ autodetection in the future.
 If set to 1 enables experimental HTTP server. This can be used to send data when
 used as an output option, or read data from a client with HTTP POST when used as
 an input option.
+If set to 2 enables experimental mutli-client HTTP server. This is not yet implemented
+in ffmpeg.c or ffserver.c and thus must not be used as a command line option.
 @example
 # Server side (sending):
 ffmpeg -i somefile.ogg -c copy -listen 1 -f ogg http://@var{server}:@var{port}

libavformat/avio.c

@@ -211,6 +211,26 @@ int ffurl_connect(URLContext *uc, AVDictionary **options)
     return 0;
 }
 
+int ffurl_accept(URLContext *s, URLContext **c)
+{
+    av_assert0(!*c);
+    if (s->prot->url_accept)
+        return s->prot->url_accept(s, c);
+    return AVERROR(EBADF);
+}
+
+int ffurl_handshake(URLContext *c)
+{
+    int ret;
+    if (c->prot->url_handshake) {
+        ret = c->prot->url_handshake(c);
+        if (ret)
+            return ret;
+    }
+    c->is_connected = 1;
+    return 0;
+}
+
 #define URL_SCHEME_CHARS                        \
     "abcdefghijklmnopqrstuvwxyz"                \
     "ABCDEFGHIJKLMNOPQRSTUVWXYZ"                \

libavformat/avio.h

@@ -648,4 +648,33 @@ struct AVBPrint;
  */
 int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size);
 
+/**
+ * Accept and allocate a client context on a server context.
+ * @param  s the server context
+ * @param  c the client context, must be unallocated
+ * @return   >= 0 on success or a negative value corresponding
+ *           to an AVERROR on failure
+ */
+int avio_accept(AVIOContext *s, AVIOContext **c);
+
+/**
+ * Perform one step of the protocol handshake to accept a new client.
+ * This function must be called on a client returned by avio_accept() before
+ * using it as a read/write context.
+ * It is separate from avio_accept() because it may block.
+ * A step of the handshake is defined by places where the application may
+ * decide to change the proceedings.
+ * For example, on a protocol with a request header and a reply header, each
+ * one can constitute a step because the application may use the parameters
+ * from the request to change parameters in the reply; or each individual
+ * chunk of the request can constitute a step.
+ * If the handshake is already finished, avio_handshake() does nothing and
+ * returns 0 immediately.
+ *
+ * @param  c the client context to perform the handshake on
+ * @return   0   on a complete and successful handshake
+ *           > 0 if the handshake progressed, but is not complete
+ *           < 0 for an AVERROR code
+ */
+int avio_handshake(AVIOContext *c);
 #endif /* AVFORMAT_AVIO_H */

libavformat/aviobuf.c

@@ -1021,6 +1021,23 @@ int avio_read_to_bprint(AVIOContext *h, AVBPrint *pb, size_t max_size)
     return 0;
 }
 
+int avio_accept(AVIOContext *s, AVIOContext **c)
+{
+    int ret;
+    URLContext *sc = s->opaque;
+    URLContext *cc = NULL;
+    ret = ffurl_accept(sc, &cc);
+    if (ret < 0)
+        return ret;
+    return ffio_fdopen(c, cc);
+}
+
+int avio_handshake(AVIOContext *c)
+{
+    URLContext *cc = c->opaque;
+    return ffurl_handshake(cc);
+}
+
 /* output in a dynamic buffer */
 
 typedef struct DynBuffer {

libavformat/http.c

@@ -25,6 +25,7 @@
 #include <zlib.h>
 #endif /* CONFIG_ZLIB */
 
+#include "libavutil/avassert.h"
 #include "libavutil/avstring.h"
 #include "libavutil/opt.h"
 
@@ -44,6 +45,14 @@
  * path names). */
 #define BUFFER_SIZE   MAX_URL_SIZE
 #define MAX_REDIRECTS 8
+#define HTTP_SINGLE   1
+#define HTTP_MUTLI    2
+typedef enum {
+    LOWER_PROTO,
+    READ_HEADERS,
+    WRITE_REPLY_HEADERS,
+    FINISH
+}HandshakeState;
 
 typedef struct HTTPContext {
     const AVClass *class;
@@ -97,6 +106,11 @@ typedef struct HTTPContext {
     char *method;
     int reconnect;
     int listen;
+    char *resource;
+    int reply_code;
+    int is_multi_client;
+    HandshakeState handshake_step;
+    int is_connected_server;
 } HTTPContext;
 
 #define OFFSET(x) offsetof(HTTPContext, x)
@@ -128,7 +142,9 @@ static const AVOption options[] = {
     { "end_offset", "try to limit the request to bytes preceding this offset", OFFSET(end_off), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, D },
     { "method", "Override the HTTP method or set the expected HTTP method from a client", OFFSET(method), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, D | E },
     { "reconnect", "auto reconnect after disconnect before EOF", OFFSET(reconnect), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, D },
-    { "listen", "listen on HTTP", OFFSET(listen), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, D | E },
+    { "listen", "listen on HTTP", OFFSET(listen), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 2, D | E },
+    { "resource", "The resource requested by a client", OFFSET(resource), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, E },
+    { "reply_code", "The http status code to return to a client", OFFSET(reply_code), AV_OPT_TYPE_INT, { .i64 = 200}, INT_MIN, 599, E},
     { NULL }
 };
 
@@ -299,51 +315,143 @@ int ff_http_averror(int status_code, int default_averror)
         return default_averror;
 }
 
-static void handle_http_errors(URLContext *h, int error)
+static int http_write_reply(URLContext* h, int status_code)
 {
-    static const char bad_request[] = "HTTP/1.1 400 Bad Request\r\nContent-Type: text/plain\r\n\r\n400 Bad Request\r\n";
-    static const char internal_server_error[] = "HTTP/1.1 500 Internal server error\r\nContent-Type: text/plain\r\n\r\n500 Internal server error\r\n";
+    int ret, body = 0, reply_code, message_len;
+    const char *reply_text, *content_type;
     HTTPContext *s = h->priv_data;
-    if (h->is_connected) {
-        switch(error) {
-            case AVERROR_HTTP_BAD_REQUEST:
-                ffurl_write(s->hd, bad_request, strlen(bad_request));
-                break;
-            default:
-                av_log(h, AV_LOG_ERROR, "Unhandled HTTP error.\n");
-                ffurl_write(s->hd, internal_server_error, strlen(internal_server_error));
+    char message[BUFFER_SIZE];
+    content_type = "text/plain";
+
+    if (status_code < 0)
+        body = 1;
+    switch (status_code) {
+    case AVERROR_HTTP_BAD_REQUEST:
+    case 400:
+        reply_code = 400;
+        reply_text = "Bad Request";
+        break;
+    case AVERROR_HTTP_FORBIDDEN:
+    case 403:
+        reply_code = 403;
+        reply_text = "Forbidden";
+        break;
+    case AVERROR_HTTP_NOT_FOUND:
+    case 404:
+        reply_code = 404;
+        reply_text = "Not Found";
+        break;
+    case 200:
+        reply_code = 200;
+        reply_text = "OK";
+        content_type = "application/octet-stream";
+        break;
+    case AVERROR_HTTP_SERVER_ERROR:
+    case 500:
+        reply_code = 500;
+        reply_text = "Internal server error";
+        break;
+    default:
+        return AVERROR(EINVAL);
+    }
+    if (body) {
+        s->chunked_post = 0;
+        message_len = snprintf(message, sizeof(message),
+                 "HTTP/1.1 %03d %s\r\n"
+                 "Content-Type: %s\r\n"
+                 "Content-Length: %zu\r\n"
+                 "\r\n"
+                 "%03d %s\r\n",
+                 reply_code,
+                 reply_text,
+                 content_type,
+                 strlen(reply_text) + 6, // 3 digit status code + space + \r\n
+                 reply_code,
+                 reply_text);
+    } else {
+        s->chunked_post = 1;
+        message_len = snprintf(message, sizeof(message),
+                 "HTTP/1.1 %03d %s\r\n"
+                 "Content-Type: %s\r\n"
+                 "Transfer-Encoding: chunked\r\n"
+                 "\r\n",
+                 reply_code,
+                 reply_text,
+                 content_type);
+    }
+    av_log(h, AV_LOG_TRACE, "HTTP reply header: \n%s----\n", message);
+    if ((ret = ffurl_write(s->hd, message, message_len)) < 0)
+        return ret;
+    return 0;
+}
+
+static void handle_http_errors(URLContext *h, int error)
+{
+    av_assert0(error < 0);
+    http_write_reply(h, error);
+}
+
+static int http_handshake(URLContext *c)
+{
+    int ret, err, new_location;
+    HTTPContext *ch = c->priv_data;
+    URLContext *cl = ch->hd;
+    switch (ch->handshake_step) {
+    case LOWER_PROTO:
+        av_log(c, AV_LOG_TRACE, "Lower protocol\n");
+        if ((ret = ffurl_handshake(cl) > 0))
+            return 2 + ret;
+        if ((ret < 0))
+            return ret;
+        ch->handshake_step = READ_HEADERS;
+        ch->is_connected_server = 1;
+        return 2;
+    case READ_HEADERS:
+        av_log(c, AV_LOG_TRACE, "Read headers\n");
+        if ((err = http_read_header(c, &new_location)) < 0) {
+            handle_http_errors(c, err);
+            return err;
         }
+        ch->handshake_step = WRITE_REPLY_HEADERS;
+        return 1;
+    case WRITE_REPLY_HEADERS:
+        av_log(c, AV_LOG_TRACE, "Reply code: %d\n", ch->reply_code);
+        if ((err = http_write_reply(c, ch->reply_code)) < 0)
+            return err;
+        ch->handshake_step = FINISH;
+        return 1;
+    case FINISH:
+        return 0;
     }
+    // this should never be reached.
+    return AVERROR(EINVAL);
 }
 
 static int http_listen(URLContext *h, const char *uri, int flags,
                        AVDictionary **options) {
     HTTPContext *s = h->priv_data;
     int ret;
-    static const char header[] = "HTTP/1.1 200 OK\r\nContent-Type: application/octet-stream\r\nTransfer-Encoding: chunked\r\n\r\n";
     char hostname[1024], proto[10];
     char lower_url[100];
     const char *lower_proto = "tcp";
-    int port, new_location;
-    s->chunked_post = 1;
+    int port;
     av_url_split(proto, sizeof(proto), NULL, 0, hostname, sizeof(hostname), &port,
                  NULL, 0, uri);
     if (!strcmp(proto, "https"))
         lower_proto = "tls";
     ff_url_join(lower_url, sizeof(lower_url), lower_proto, NULL, hostname, port,
                 NULL);
-    av_dict_set(options, "listen", "1", 0);
+    if ((ret = av_dict_set_int(options, "listen", s->listen, 0)) < 0)
+        goto fail;
     if ((ret = ffurl_open(&s->hd, lower_url, AVIO_FLAG_READ_WRITE,
                           &h->interrupt_callback, options)) < 0)
         goto fail;
-    if ((ret = http_read_header(h, &new_location)) < 0)
-         goto fail;
-    if ((ret = ffurl_write(s->hd, header, strlen(header))) < 0)
-         goto fail;
-    return 0;
-
+    s->handshake_step = LOWER_PROTO;
+    if (s->listen == HTTP_SINGLE) { /* single client */
+        s->reply_code = 200;
+        while ((ret = http_handshake(h)) > 0);
+    }
 fail:
-    handle_http_errors(h, ret);
     av_dict_free(&s->chained_options);
     return ret;
 }
@@ -389,6 +497,26 @@ static int http_open(URLContext *h, const char *uri, int flags,
     return ret;
 }
 
+static int http_accept(URLContext *s, URLContext **c)
+{
+    int ret;
+    HTTPContext *sc = s->priv_data;
+    HTTPContext *cc;
+    URLContext *sl = sc->hd;
+    URLContext *cl = NULL;
+
+    av_assert0(sc->listen);
+    if ((ret = ffurl_alloc(c, s->filename, s->flags, &sl->interrupt_callback)) < 0)
+        goto fail;
+    cc = (*c)->priv_data;
+    if ((ret = ffurl_accept(sl, &cl)) < 0)
+        goto fail;
+    cc->hd = cl;
+    cc->is_multi_client = 1;
+fail:
+    return ret;
+}
+
 static int http_getc(HTTPContext *s)
 {
     int len;
@@ -583,7 +711,7 @@ static int process_line(URLContext *h, char *line, int line_count,
 
     p = line;
     if (line_count == 0) {
-        if (s->listen) {
+        if (s->is_connected_server) {
             // HTTP method
             method = p;
             while (!av_isspace(*p))
@@ -604,6 +732,8 @@ static int process_line(URLContext *h, char *line, int line_count,
                            "(%s autodetected %s received)\n", auto_method, method);
                     return ff_http_averror(400, AVERROR(EIO));
                 }
+                if (!(s->method = av_strdup(method)))
+                    return AVERROR(ENOMEM);
             }
 
             // HTTP resource
@@ -614,6 +744,8 @@ static int process_line(URLContext *h, char *line, int line_count,
                 p++;
             *(p++) = '\0';
             av_log(h, AV_LOG_TRACE, "Requested resource: %s\n", resource);
+            if (!(s->resource = av_strdup(resource)))
+                return AVERROR(ENOMEM);
 
             // HTTP version
             while (av_isspace(*p))
@@ -1353,6 +1485,8 @@ HTTP_CLASS(http);
 URLProtocol ff_http_protocol = {
     .name                = "http",
     .url_open2           = http_open,
+    .url_accept          = http_accept,
+    .url_handshake       = http_handshake,
     .url_read            = http_read,
     .url_write           = http_write,
     .url_seek            = http_seek,

libavformat/network.c

@@ -187,12 +187,11 @@ int ff_socket(int af, int type, int proto)
     return fd;
 }
 
-int ff_listen_bind(int fd, const struct sockaddr *addr,
-                   socklen_t addrlen, int timeout, URLContext *h)
+int ff_listen(int fd, const struct sockaddr *addr,
+              socklen_t addrlen)
 {
     int ret;
     int reuse = 1;
-    struct pollfd lp = { fd, POLLIN, 0 };
     if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuse, sizeof(reuse))) {
         av_log(NULL, AV_LOG_WARNING, "setsockopt(SO_REUSEADDR) failed\n");
     }
@@ -203,6 +202,13 @@ int ff_listen_bind(int fd, const struct sockaddr *addr,
     ret = listen(fd, 1);
     if (ret)
         return ff_neterrno();
+    return ret;
+}
+
+int ff_accept(int fd, int timeout, URLContext *h)
+{
+    int ret;
+    struct pollfd lp = { fd, POLLIN, 0 };
 
     ret = ff_poll_interrupt(&lp, 1, timeout, &h->interrupt_callback);
     if (ret < 0)
@@ -211,15 +217,24 @@ int ff_listen_bind(int fd, const struct sockaddr *addr,
     ret = accept(fd, NULL, NULL);
     if (ret < 0)
         return ff_neterrno();
-
-    closesocket(fd);
-
     if (ff_socket_nonblock(ret, 1) < 0)
         av_log(NULL, AV_LOG_DEBUG, "ff_socket_nonblock failed\n");
 
     return ret;
 }
 
+int ff_listen_bind(int fd, const struct sockaddr *addr,
+                   socklen_t addrlen, int timeout, URLContext *h)
+{
+    int ret;
+    if ((ret = ff_listen(fd, addr, addrlen)) < 0)
+        return ret;
+    if ((ret = ff_accept(fd, timeout, h)) < 0)
+        return ret;
+    closesocket(fd);
+    return ret;
+}
+
 int ff_listen_connect(int fd, const struct sockaddr *addr,
                       socklen_t addrlen, int timeout, URLContext *h,
                       int will_try_next)

libavformat/network.h

@@ -254,6 +254,26 @@ int ff_listen_bind(int fd, const struct sockaddr *addr,
                    socklen_t addrlen, int timeout,
                    URLContext *h);
 
+/**
+ * Bind to a file descriptor to an address without accepting connections.
+ * @param fd      First argument of bind().
+ * @param addr    Second argument of bind().
+ * @param addrlen Third argument of bind().
+ * @return        0 on success or an AVERROR on failure.
+ */
+int ff_listen(int fd, const struct sockaddr *addr, socklen_t addrlen);
+
+/**
+ * Poll for a single connection on the passed file descriptor.
+ * @param fd      The listening socket file descriptor.
+ * @param timeout Polling timeout in milliseconds.
+ * @param h       URLContext providing interrupt check
+ *                callback and logging context.
+ * @return        A non-blocking file descriptor on success
+ *                or an AVERROR on failure.
+ */
+int ff_accept(int fd, int timeout, URLContext *h);
+
 /**
  * Connect to a file descriptor and poll for result.
  *

libavformat/tcp.c

@@ -19,6 +19,7 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 #include "avformat.h"
+#include "libavutil/avassert.h"
 #include "libavutil/parseutils.h"
 #include "libavutil/opt.h"
 #include "libavutil/time.h"
@@ -44,7 +45,7 @@ typedef struct TCPContext {
 #define D AV_OPT_FLAG_DECODING_PARAM
 #define E AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {
-    { "listen",          "Listen for incoming connections",  OFFSET(listen),         AV_OPT_TYPE_INT, { .i64 = 0 },     0,       1,       .flags = D|E },
+    { "listen",          "Listen for incoming connections",  OFFSET(listen),         AV_OPT_TYPE_INT, { .i64 = 0 },     0,       2,       .flags = D|E },
     { "timeout",     "set timeout (in microseconds) of socket I/O operations", OFFSET(rw_timeout),     AV_OPT_TYPE_INT, { .i64 = -1 },         -1, INT_MAX, .flags = D|E },
     { "listen_timeout",  "Connection awaiting timeout (in milliseconds)",      OFFSET(listen_timeout), AV_OPT_TYPE_INT, { .i64 = -1 },         -1, INT_MAX, .flags = D|E },
     { NULL }
@@ -125,12 +126,17 @@ static int tcp_open(URLContext *h, const char *uri, int flags)
         goto fail;
     }
 
-    if (s->listen) {
-        if ((ret = ff_listen_bind(fd, cur_ai->ai_addr, cur_ai->ai_addrlen,
-                                  s->listen_timeout, h)) < 0) {
+    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 ((fd = ff_listen_bind(fd, cur_ai->ai_addr, cur_ai->ai_addrlen,
+                                 s->listen_timeout, h)) < 0) {
+            ret = fd;
             goto fail1;
         }
-        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) {
@@ -163,6 +169,22 @@ static int tcp_open(URLContext *h, const char *uri, int flags)
     return ret;
 }
 
+static int tcp_accept(URLContext *s, URLContext **c)
+{
+    TCPContext *sc = s->priv_data;
+    TCPContext *cc;
+    int ret;
+    av_assert0(sc->listen);
+    if ((ret = ffurl_alloc(c, s->filename, s->flags, &s->interrupt_callback)) < 0)
+        return ret;
+    cc = (*c)->priv_data;
+    ret = ff_accept(sc->fd, sc->listen_timeout, s);
+    if (ret < 0)
+        return ff_neterrno();
+    cc->fd = ret;
+    return 0;
+}
+
 static int tcp_read(URLContext *h, uint8_t *buf, int size)
 {
     TCPContext *s = h->priv_data;
@@ -223,6 +245,7 @@ static int tcp_get_file_handle(URLContext *h)
 URLProtocol ff_tcp_protocol = {
     .name                = "tcp",
     .url_open            = tcp_open,
+    .url_accept          = tcp_accept,
     .url_read            = tcp_read,
     .url_write           = tcp_write,
     .url_close           = tcp_close,

libavformat/url.h

@@ -58,6 +58,8 @@ typedef struct URLProtocol {
      * for those nested protocols.
      */
     int     (*url_open2)(URLContext *h, const char *url, int flags, AVDictionary **options);
+    int     (*url_accept)(URLContext *s, URLContext **c);
+    int     (*url_handshake)(URLContext *c);
 
     /**
      * Read data from the protocol.
@@ -139,6 +141,29 @@ int ffurl_connect(URLContext *uc, AVDictionary **options);
 int ffurl_open(URLContext **puc, const char *filename, int flags,
                const AVIOInterruptCB *int_cb, AVDictionary **options);
 
+/**
+ * Accept an URLContext c on an URLContext s
+ *
+ * @param  s server context
+ * @param  c client context, must be unallocated.
+ * @return >= 0 on success, ff_neterrno() on failure.
+ */
+int ffurl_accept(URLContext *s, URLContext **c);
+
+/**
+ * Perform one step of the protocol handshake to accept a new client.
+ * See avio_handshake() for details.
+ * Implementations should try to return decreasing values.
+ * If the protocol uses an underlying protocol, the underlying handshake is
+ * usually the first step, and the return value can be:
+ * (largest value for this protocol) + (return value from other protocol)
+ *
+ * @param  c the client context
+ * @return >= 0 on success or a negative value corresponding
+ *         to an AVERROR code on failure
+ */
+int ffurl_handshake(URLContext *c);
+
 /**
  * Read up to size bytes from the resource accessed by h, and store
  * the read bytes in buf.