能否用ActionCable接收TCP数据？Rails 5应用技术咨询

Great question! Let's break this down clearly for your Rails 5 project:

Short answer: No, not directly. ActionCable is built specifically for WebSocket connections, which are a layer on top of TCP—they require an HTTP handshake and follow a specific frame format. If your external sender is sending raw, unformatted TCP data (not wrapped in WebSocket protocol), ActionCable won't recognize or process it.

That said, if you can get the external party to adjust their sender to use WebSocket instead of raw TCP, ActionCable works perfectly. But for pure TCP streams, it's not the right tool.

Absolutely. EventMachine is the go-to Ruby library for handling asynchronous TCP/UDP I/O, and it integrates smoothly with Rails 5. It's designed to efficiently handle persistent TCP connections and incoming data streams, which is exactly what you need here.

Here's a simple skeleton to get you started. Create a file like lib/tcp_stream_handler.rb:

require 'eventmachine'

class TCPStreamHandler < EventMachine::Connection
  def receive_data(raw_data)
    # Process the incoming TCP data (parse, validate, etc.)
    processed_data = raw_data.strip

    # Safely interact with Rails models (EventMachine runs in its own thread)
    ActiveRecord::Base.connection_pool.with_connection do
      # Store data in your Rails database
      IncomingTcpRecord.create(payload: processed_data)
      
      # Optional: Broadcast to ActionCable if you need real-time updates
      ActionCable.server.broadcast('tcp_stream_channel', data: processed_data)
    end

    # Optional: Send a response back to the sender
    send_data("Acknowledged: #{processed_data.length} bytes received\n")
  end

  def unbind
    puts "TCP connection closed"
  end
end

# Method to start the server
def start_tcp_server
  EventMachine.run do
    # Listen on port 9000 (adjust to your needs)
    EventMachine.start_server('0.0.0.0', 9000, TCPStreamHandler)
    puts "TCP stream server running on port 9000"
  end
end

To start this alongside your Rails app, you can add an initializer (e.g., config/initializers/tcp_server.rb) with:

# Start the TCP server in a background thread when Rails boots
Thread.new { start_tcp_server }

Or run it separately with rails runner lib/tcp_stream_handler.rb if you prefer to manage it as a standalone process.

While there aren't many public "out-of-the-box" Rails apps demonstrating this exact use case, EventMachine is widely used in production Ruby systems for TCP handling. You can adapt examples from the EventMachine documentation, focusing on thread-safe interactions with Rails (like using connection_pool.with_connection for database operations) to build your solution.

• If the external sender can't switch to WebSocket: Use EventMachine to build your TCP receiver, then bridge the data into Rails (database storage, ActionCable broadcasts, etc.).
• If the external sender can use WebSocket: Stick with ActionCable—it's more integrated with Rails and requires less custom code.

内容的提问来源于stack exchange，提问作者anthonyms