### Server Example: Echo Server

Source: https://rubydoc.info/gems/eventmachine

A basic example demonstrating how to set up a simple echo server using EventMachine. This server listens for incoming connections and echoes back any data received.

```APIDOC
## Server Example: Echo Server

### Description
This example demonstrates a basic echo server using EventMachine. It listens on a specified port and echoes back any data received from clients.

### Code
```ruby
require 'eventmachine'

class EchoServer < EM::Connection
  def receive_data(data)
    send_data data
  end
end

EM.run {
  EM.start_server '127.0.0.1', 8080, EchoServer
  puts 'Echo server started on port 8080'
}
```

### How to Run
1. Save the code as `echo_server.rb`.
2. Run the script using `ruby echo_server.rb`.
3. Connect to `127.0.0.1:8080` using a tool like `telnet` or `netcat` and send data.
```

--------------------------------

### Install EventMachine Gem

Source: https://rubydoc.info/gems/eventmachine

Install the EventMachine gem using RubyGems.

```bash
gem install eventmachine
```

--------------------------------

### EventMachine Echo Server Example

Source: https://rubydoc.info/gems/eventmachine

A fully-functional echo server written with EventMachine. This example demonstrates basic connection handling, data reception, and sending data back to the client. It will block the current thread.

```ruby
 require 'eventmachine'

 module EchoServer
   def post_init
     puts "-- someone connected to the echo server!"
   end

   def receive_data data
     send_data ">>>you sent: #{data}"
     close_connection if data =~ /quit/i
   end

   def unbind
     puts "-- someone disconnected from the echo server!"
   end
end

# Note that this will block current thread.
EventMachine.run {
  EventMachine.start_server "127.0.0.1", 8081, EchoServer
}
```

--------------------------------

### Add EventMachine to Gemfile

Source: https://rubydoc.info/gems/eventmachine

Add the EventMachine gem to your Gemfile if you are using Bundler.

```ruby
gem "eventmachine"
```

--------------------------------

### What is EventMachine

Source: https://rubydoc.info/gems/eventmachine

EventMachine is an event-driven I/O and lightweight concurrency library for Ruby. It utilizes the Reactor pattern for event-driven I/O, similar to libraries like Node.js and Python's Twisted. Its primary goals are to provide extreme scalability, performance, and stability while simplifying the complexities of threaded network programming.

```APIDOC
## What is EventMachine

### Description
EventMachine is an event-driven I/O and lightweight concurrency library for Ruby that uses the Reactor pattern. It is designed for high scalability, performance, and stability, while simplifying network programming.

### Use Cases
- Scalable event-driven servers (e.g., Thin, Goliath)
- Asynchronous clients for protocols and APIs (e.g., em-http-request, amqp)
- Efficient network proxies
- File and network monitoring tools
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.