我在线聊天。它使用房间。如果用户发送消息而另一个用户不在线，则应增加“遗漏消息”计数器。我尝试使用setTimeout创建超时，如果它们发出事件，则会清除该超时。
然而，chatOnline并未按预期启动，这导致它始终报告用户处于离线状态并递增missed_texts中rethinkdb列的计数器（未显示）因为它不相关）。
如何从socket.io中检索用户是否在线？我的目标是避免在数据库中存储状态信息，这可能会很快失控。
我试过的代码：
socket.on('chatSend',function(data){
if(socket.client.user.room_id !== null){
//were storing some crap in the socket object for easy retrieval.
data.user_id = socket.client.user.id;
data.room_id = socket.client.user.room_id;
data.timestamp = ~~(new Date() / 1000);
//insert message into chat table
r.table('chat').insert(data).run().then(function(res){
//retrive generated record from table
r.table('chat').get(res.generated_keys[0]).run().then(function(data2){
io.sockets.in(data2.room_id).emit('chatNew',data);//emit to all users in room
log('chatSend');
//attempt to see if the other user is online
getOtherUser(data2.room_id,socket.client.user.id,function(tid){
log('other user id: %d',tid);
//all users automatically join a room matching their user id when connecting.
//unsure how to see if the user is online. this doesnt work.
//this is what i need help with. retrieving the other users socket resource if they are online,
//and if they are not then return null or false, etc so i can work with that.
var othersocket = io.sockets.in(tid);
//if timeout completes before they respond, they are not online.
var tmptime = setTimeout(function(){
log('other user not online.');
othersocket.removeListener('chatOnline',tmpfunc);
missedTexts(data2.room_id,tid,'INCR');
},5000);
var tmpfunc = function(){
clearTimeout(tmptime);
//remove the listener
othersocket.removeListener('chatOnline',tmpfunc);
};
//emit chatOnline to other user socket
//when they respond, cleartimeout, resulting in counter not being incremented.
othersocket.on('chatOnline',tmpfunc);
othersocket.emit('chatOnline');
});
});
});
}
});