Prevent socket io from emitting ping timeout for inactive or not focused browser page in mobile browsers chrome, firefox and safari. · Issue #3507 · socketio/socket.io · GitHub
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socket.io CDN by jsDelivr - A CDN for npm and GitHub
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One article is enough to understand modern web-side instant messaging technology: WebSocket, socket.io, SSE - 即时通讯开发 - SegmentFault 思否
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