Node.js ssh won't run again

I have three Ubuntu servers, let's call them A, B, C. On server A, I have installed node.js and socket.io. On server B, I have installed apache and php. I would like to send a socket.io event through php from server B to server A. When the event is fired, server A would ssh to server C and run the 'reboot' command.

I have successfully set node.js up.

var Connection = require("ssh2");
var sys = require("sys");
var exec = require("child_process").exec;
var io = require("socket.io").listen(81);
var c = new Connection();

c.on("connect", function(){
    console.log("Connection :: connect");
});

c.on("ready", function(){
    console.log("Connection :: ready");
    c.exec("reboot", function(err, stream){
            if(err) throw err;
            stream.on("data", function(data, extended){
                    console.log((extended === "stderr" ? "STDERR: " : "STDOUT: ") + data);
            });
            stream.on("end", function(){
                    console.log("Stream :: EOF");
            });
            stream.on("close", function(){
                    console.log("Stream :: close");
            });
            stream.on("exit", function(code, signal){
                    console.log("Stream :: exit :: code: " + code + ", signal: " + signal);
                    c.end();
            });
    });
});

c.on("error", function(err){
    console.log("Connection :: error :: " + err);
});

c.on("end", function(){
    console.log("Connection :: end");
});

c.on("close", function(had_error){
    console.log("Console :: close");
});

io.sockets.on("connection", function (socket) {
    socket.on("my_event", function (data) {
        c.connect({
           host: data.ip,
           port: 22,
           username: "root",
           privateKey: require("fs").readFileSync("/root/.ssh/id")
        });
    });
});

I can send the event successfully, and server C restarts, but I can only send the event once. On the second attempt the request won't reach the 'ready' state. It can be seen in the log:

info  - socket.io started
debug - client authorized .......
Connection :: connect
debug - got disconnection packet ......
Connection :: ready
Stream :: exit :: code: 0, signal: undefined
Stream :: EOF
Stream :: close
Connection :: end
Console :: close

debug - client authorized .......
Connection :: connect
debug - got disconnection packet ......
Connection :: end
Console :: close

What shall I do?