ReplyError: Ready check failed: ERR max number of clients reached in Node.js

I'm a newbie in Node.js and I tried to node app.js to hold client but it gives me an error with this message below,

events.js:141
      throw er; // Unhandled 'error' event
      ^
ReplyError: Ready check failed: ERR max number of clients reached
    at parseError (/opt/smarthome/node_modules/redis-parser/lib/parser.js:181:12)
    at parseType (/opt/smarthome/node_modules/redis-parser/lib/parser.js:291:14)

It worked well last week but after I disconnect and back to it, it gives me an error like above...

Also, here is my Node.js code

io.sockets.addListener('connection', function(socket){
    console.log("connceted : " + socket.id);

    var subscriber = redis.createClient(6379, 'localhost');
    subscriber.psubscribe("*");
    subscriber.on("pmessage", function(pattern, channel, message) {
        //console.log(message);
        socket.emit(channel, message);
    });

    socket.on('disconnect', function () {
        console.log("disconnceted : " + socket.id);
        subscriber.quit();
    });

    socket.on('close', function() {
        console.log("close");
        subscriber.quit();
    });
});

server.listen(3000);


// Scheduler - DashBoard Update every 5 minutes
var testInterval = setInterval(function(){
        channelCheck = "" ;
},300000);

// Reading JSON data of Dashboard
var front       = fs_Dash.readFileSync('./dashboard_json/front.json', 'utf8');
var jsonContents = fs_Dash.readFileSync('./dashboard_json/jsoncontent.json', 'utf8');
var behind      = fs_Dash.readFileSync('./dashboard_json/behind.json', 'utf8');

// Starting subscribe
subscriber.on("pmessage", function(pattern, channel, message) {

            // Reading subscribe data
    var s_data = JSON.parse(message);
    var node_id = JSON.stringify(s_data.node_info[0].id).replace(/\"/g, "");
    channel = channel.toUpperCase();

    // Creating Channels data
    openfile = fs_Dash.open('./sensor/'+channel+'.txt', 'a', function(err, fd) {
        fs_Dash.close(fd);
    });


    // Reading Channels data
    fs_Dash.readFile('./sensor/'+channel+'.txt', 'utf8', function(err, data) {

        // Checking sensors list
        sensor_list=JSON.stringify(data);
        if(sensor_list == null) sensor_list = "";
        sensors = sensor_list.replace(/\\n/g," ").replace(/\:/g, "").replace(/\"/g,"").split(' ');
        alljson = front.replace('EXTITLE',channel);
        for (var i = 0 ; i < sensors.length ; i++){
            alljson += jsonContents.replace(/SENSORS/gi,channel+"_"+sensors[i].replace(/\"/g,""));
            if(i >= sensors.length -2){
                break;
            }
            alljson += ',';
        }

        // Updating Dashboard version
        alljson += behind.replace('XXX', schemaVersion).replace('VVV', version);
        version += 1;
        schemaVersion += 1;

        // Setting Request options
        options = {
            url: 'my private url',
            headers: {
                'Authorization' : "Basic " + new Buffer('hi' + ":" + 'hi').toString('base64'),
                'Content-Type' : 'application/json',
                'Accept' : 'application/json'
            },
            body: alljson
        };

        // Discovering a NEW channel => Updating Dashboard
        if(JSON.stringify(channelCheck).search(channel) == -1){
                request_Dash.post(options, function(err, res, body) {
                    console.log("renew dashboard");
                });
                channelCheck += channel+',';
            }

                            // Discovering a NEW sensor => Updating Dashboard, Writing Sensor Data
        if ((sensor_list).search(node_id)==-1){

            // Sending post Dashboard generating message
            request_Dash.post(options, function(err, res, body) {
                console.log('status code : ' + res);
                console.log("renew dashboard");
            });

            // Writing Channels and Sensor data
            fs_Dash.appendFile('./sensor/'+channel+'.txt', node_id+'\n', function(err) {
                if(err) throw err;
                   // console.log('File write completed');
            });
        }

    });
    //fs_Dash.close();
});

subscriber.psubscribe('*');

What's wrong with this..??

Does anybody have a solution for this..??

Thanks in advance.

via paulc1111