learnyounode/exercises/time_server/problem.md

Learn You The Node.js For Much Win! An intro to Node.js via a set of self-guided workshops.

Create a file named `time-server.js`.

Write a **TCP time server**!

Your server should listen to TCP connections on the port provided by the first argument to your program. For each connection you must write the current date & 24 hour time in the format:

```
"YYYY-MM-DD hh:mm"
```

followed by a **newline** character. Month, day, hour and minute must be *zero-filled* to 2 integers. For example:

```
"2013-07-06 17:42"
```

After sending the string, close the connection.

----------------------------------------------------------------------
## HINTS

For this exercise we'll be creating a raw TCP server. There's no HTTP involved here so we need to use the `net` module from Node core which has all the basic networking functions.

The `net` module has a method named `net.createServer()` that takes a function. The function that you need to pass to `net.createServer()` is a connection listener that is called more than once. Every connection received by your server triggers another call to the listener. The listener function has the signature:

```js
function listener (socket) { /* ... */ }
```

`net.createServer()` also returns an instance of your `server`. You must call `server.listen(portNumber)` to start listening on a particular port.

A typical Node TCP server looks like this:

```js
const net = require('net')
const server = net.createServer(function (socket) {
  // socket handling logic
})
server.listen(8000)
```

Remember to use the port number supplied to you as the first command-line argument.

The `socket` object contains a lot of meta-data regarding the connection, but it is also a Node duplex Stream, in that it can be both read from, and written to. For this exercise we only need to write data and then close the socket.

Use `socket.write(data)` to write data to the socket and `socket.end()` to close the socket. Alternatively, the `.end()` method also takes a data object so you can simplify to just: `socket.end(data)`.

Documentation on the `net` module can be found by pointing your browser here:

  {rootdir:/docs-nodejs/net.html}

To create the date, you'll need to create a custom format from a `new Date()` object. The methods that will be useful are:

```js
date.getFullYear()
date.getMonth() // starts at 0
date.getDate() // returns the day of month
date.getHours()
date.getMinutes()
```

Or, if you want to be adventurous, use the `strftime` package from npm. The `strftime(fmt, date)` function takes date formats just like the unix `date` command. You can read more about strftime at: https://github.com/samsonjs/strftime

Check to see if your program is correct by running this command:

```sh
$ {appname} verify time-server.js
```