Socket.io 1.7.3(+) or later:
function getConnectedList () { let list = [] for ( let client in io.sockets.connected ) { list.push(client) } return list } console.log( getConnectedList() ) // returns [ 'yIfhb2tw7mxgrnF6AAAA', 'qABFaNDSYknCysbgAAAB' ] function getConnectedList () { let list = [] for (let client in io.sockets.connected) { list.push(client) } return list } console.log(getConnectedList()) // returns [ 'yIfhb2tw7mxgrnF6AAAA', 'qABFaNDSYknCysbgAAAB' ]