SSDPResponder implements the Simple Service Discovery Protocol for UPnP.

The SSDPResponder maintains a list of local Advertisements and periodically sends out discovery messages, using a multicast socket. It also processes discovery and search messages received from other UPnP devices on the network. Search messages are replied to, if possible, while discovery messages (ssdp:alive and ssdp:byebye) from other UPnP devices are made available via events.

The steps for setting up a SSDPResponder are as follows:

// 1. Set up a multicast socket (we use a wildcard address here)
Poco::Net::SocketAddress sa(Poco::Net::IPAddress(), Poco::UPnP::SSDPResponder::MULTICAST_PORT);
Poco::Net::MulticastSocket socket(sa);
socket.setLoopback(true); // optional
socket.setTimeToLive(4);  // recommended by SSDP specification
// 2. Set up SSDPResponder
Poco::UPnP::SSDPResponder responder(socket);
// 3. Join multicast group for advertisements
socket.joinGroup(responder.groupAddress().host());
// 4. Publish local devices and services.
responder.publish(pRootDeviceAdvertisement);
...
// 5. Start responder
responder.start();

To shutdown a SSDPResponder, stop it and leave the multicast group:

responder.stop();
socket.leaveGroup(responder.groupAddress().host());

According to the UPnP SSDP specification, when a device is added to the network, it multicasts discovery messages to advertise its root device, any embedded devices, and any services. Each discovery message contains four major components:

1. a potential search target (e.g., device type), sent in an NT (Notification Type) header,
2. a composite identifier for the advertisement, sent in a USN (Unique Service Name) header,
3. a URL for more information about the device (or enclosing device in the case of a service), sent in a LOCATION header, and
4. a duration for which the advertisement is valid, sent in a CACHE-CONTROL header.

To advertise its capabilities, a device multicasts a number of discovery messages. Specifically, a root device must multicast:

• Three discovery messages (root device, device UUID and device type) for the root device.
• Two discovery messages (device UUID and device type) for each embedded device.
• One discovery message (service type) for each service type in each device.

For more information, please refer to the UPnP Device Architecture specification.

Creates a SSDPResponder, using the given multicast socket, which must have been properly setup.

Creates a SSDPResponder, using the given multicast socket, which must have been properly setup. Multicast messages are sent to the given address. Use of a non-standard multicast address (239.255.255.250:1900) is not recommended.

Creates a SSDPResponder, using the given timer and multicast socket, which must have been properly setup.

Creates a SSDPResponder, using the given timer and multicast socket, which must have been properly setup. Multicast messages are sent to the given address. Use of a non-standard multicast address (239.255.255.250:1900) is not recommended.

Destroys the SSDPResponder.

Stops the responder if it is still running.

Returns the maximum response time (in seconds) sent with search requests. The default is 2 seconds.

Returns the Server identification string sent with alive messages.

Returns the socket address of the multicast group used by this SSDPResponder.

Unless an address has been given in the constructor, the default SSDP multicast address (239.255.255.250:1900) is returned.

Adds a new Advertisement to the SSDPResponder's list of local advertisements.

An Advertisement can be for a root device, a device UUID, a device type or a service type.

If the SSDPResponder is already running, will also send an initial ssdp:alive message. While the SSDPResponder is running, it will send periodic discovery messages (ssdp:alive) for the Advertisement.

Throws a Poco::ExistsException if an Advertisement with the same USN has already been advertized.

Removes the Advertisement with the given Unique Service Name.

If the SSDPResponder is running, will send a ssdp:byebye message for the given USN.

Throws a Poco::NotFoundException if an Advertisement with the given USN is unknown.

Multicasts a search request for the given search target.

According to the SSDP specification, the search target can be one of:

• ssdp:all: Search for all devices and services.
• upnp:rootdevice: Search for all root devices.
• a Unique Service Name: Search for a specific device or service type.

Sets the maximum response time (in seconds) sent with search requests.

The maximum response time must be greater than 0.

Sets the Server identification string sent with alive message.

The format must be <os>/<version> UPnP/1.0 <product>/<version>.

Starts the SSDPResponder.

The responder will start receiving advertisements. It will also send ssdp:alive messages for all registered advertisements.

While the SSDPResponder is running, it will send periodic discovery messages (ssdp:alive) for all registered advertisements. Messages will be send at a random interval. The interval will be larger than 1/3 of the Advertisement's life time and smaller than 2/3 of the Advertisement's life time.

The SSDPResponder will also reply to any matching search requests it receives.

Stops the SSDPResponder.

The responder will send ssdp:byebye messages for all registered advertisements.

A ssdp:byebye message has been received for the given Unique Service Name (USN).

The event handler should return as soon as possible to avoid disruptions in SSDP message processing.

A ssdp:alive message has been received for the given Advertisement.

The Advertisement will contain the following attributes:

• Host: the host address and port number (<host>:<port>) of the device sending the message.
• Server: the server name (the value of the Server header sent with the ssdp:alive message). Will not be included in advertisements from search responses.
• ST: the search target. Only included in advertisements from search responses.

The event handler should return as soon as possible to avoid disruptions in SSDP message processing.