[docs] Updating the explicit information for binding to IPv6 wildcard (…

…#2765).

docs/API/API-functions.md

@@ -359,8 +359,12 @@ int srt_bind(SRTSOCKET u, const struct sockaddr* name, int namelen);
 Binds a socket to a local address and port. Binding specifies the local network
 interface and the UDP port number to be used for the socket. When the local 
 address is a wildcard (`INADDR_ANY` for IPv4 or `in6addr_any` for IPv6), then
-it's bound to all interfaces (although see `SRTO_IPV6ONLY` and additional
-information below for details about the wildcard address in IPv6).
+it's bound to all interfaces.
+
+**IMPORTANT**: When you bind an IPv6 wildcard address, note that the
+`SRTO_IPV6ONLY` option must be set on the socket explicitly to 1 or 0 prior to
+calling this function. See
+[`SRTO_IPV6ONLY`](API-socket-options.md#SRTO_IPV6ONLY) for more details.
 
 Binding is necessary for every socket to be used for communication. If the socket
 is to be used to initiate a connection to a listener socket, which can be done,

docs/API/API-socket-options.md

@@ -647,10 +647,22 @@ and the actual value for connected sockets.
 
 Set system socket option level `IPPROTO_IPV6` named `IPV6_V6ONLY`. This is meaningful
 only when the socket is going to be bound to the IPv6 wildcard address `in6addr_any`
-(known also as `::`). In this case this option must be also set explicitly to 0 or 1
-before binding, otherwise binding will fail (this is because it is not possible to
-determine the default value of this above-mentioned system option in any portable or
-reliable way). Possible values are:
+(known also as `::`). If you bind to a wildcard address, you have the following
+possibilities:
+
+* IPv4 only: bind to an IPv4 wildcard address
+* IPv6 only: bind to an IPv6 wildcard address and set this option to 1
+* IPv4 and IPv6: bind to an IPv6 wildcard address and set this option to 0
+
+This option's default value is -1 because it is not possible to determine the default 
+value on the current platform, and if you bind to an IPv6 wildcard address, this value 
+is required prior to binding. When you bind implicitly by calling `srt_connect` on the 
+socket, this isn't a problem -- binding will be done using the system-default value and then
+extracted afterwards. But if you want to bind explicitly using `srt_bind`, this
+option must be set explicitly to 0 or 1 because this information is vital for
+determining any potential bind conflicts with other sockets.
+
+Possible values are:
 
 * -1: (default) use system-default value (can be used when not binding to IPv6 wildcard `::`)
 * 0: The binding to `in6addr_any` will bind to both IPv6 and IPv4 wildcard address

docs/apps/srt-live-transmit.md

@@ -285,11 +285,13 @@ specify the host as `::`.
 NOTE: Don't use square brackets syntax in the **adapter** parameter
 specification, as in this case only the host is expected.
 
-3. If you want to listen for connections from both IPv4 and IPv6, mind the
-`ipv6only` option. The default value for this option is system default (see
-system manual for `IPV6_V6ONLY` socket option); if unsure, you might want to
-enforce `ipv6only=0` in order to be able to accept both IPv4 and IPv6
-connections by the same listener, or set `ipv6only=1` to accept exclusively IPv6.
+3. If you bind to an IPv6 wildcard address (with listener mode, or when using the `bind`
+option), setting the `ipv6only` option to 0 or 1 is obligatory, as it is a part
+of the binding definition. If you set it to 1, the binding will apply only to
+IPv6 local addresses, and if you set it to 0, it will apply to both IPv4 and
+IPv6 local addresses. See the
+[`SRTO_IPV6ONLY`](../API/API-socket-options.md#SRTO_IPV6ONLY) option
+description for details.
 
 4. In rendezvous mode you may only interconnect both parties using IPv4, 
 or both using IPv6. Unlike listener mode, if you want to leave the socket
@@ -303,9 +305,8 @@ Examples:
 
 * `srt://[::]:5000` defines caller mode (!) with IPv6.
 
-* `srt://[::]:5000?mode=listener` defines listener mode with IPv6. If the
-    default value for `IPV6_V6ONLY` system socket option is 0, it will accept
-    also IPv4 connections.
+* `srt://[::]:5000?mode=listener&ipv6only=1` defines listener mode with IPv6.
+    Only connections from IPv6 callers will be accepted.
 
 * `srt://192.168.0.5:5000?mode=rendezvous` will make a rendezvous connection
     with local address `INADDR_ANY` (IPv4) and port 5000 to a destination with