Services over wireless communication with high flexibility and efficiency

A media playback device, comprising:

• a processor;
• and
• a memory storing computer program instructions that, when executed by the processor, cause the media playback device to perform a playback method comprising:
• performing a discovery process to discover a cast device over a wireless local area network, wherein the cast device is configured to determine a media playback device as a cast destination for cast of a media content item and cast the media content item to the determined media playback device;
• in response to a cast request message for the media playback device from the discovered cast device over the wireless local area network, fetching streaming of the requested media content item;
• and
• playing back the streamed media content item.

A user device, comprising:

• an audio input;
• an audio output;
• a processor;
• and
• a memory storing computer program instructions that, when executed by the processor, cause the user device to perform a public address method comprising:
• setting the user device as one of a microphone device and speaker device in a public address system;
• when the user device is set as the microphone device, activating the audio input and deactivating the audio output, and discovering another user device set as the speaker device over a wireless local area network to cast an audio stream to the discovered another user device over the wireless local area network, wherein the audio stream is generated based on voice inputted through the activated audio input;
• and
• when the user device set as the speaker device, activating the audio output and deactivating the audio input, and discovering another user device set as the microphone device over the wireless local area network to receive cast of an audio stream from the discovered another user device over the wireless local area network and output sound based on the audio stream through the activated audio output, wherein the audio stream is generated and casted by the discovered another user device over the wireless local area network.