## 问题 Problem 你希望网络中能有一个持久的服务，能够与它的客户端保持一个持续的链接。 You want to provide a persistent service over a network, one which maintains an on-going connection with a client. ## 方法 Solution 创建一个双向通信的TCP服务器。 Create a bi-directional TCP server. ### 用Node.js In Node.js ~~~ net = require 'net' domain = 'localhost' port = 9001 server = net.createServer (socket) -> console.log "New connection from #{socket.remoteAddress}" socket.on 'data', (data) -> console.log "#{socket.remoteAddress} sent: #{data}" others = server.connections - 1 socket.write "You have #{others} #{others == 1 and "peer" or "peers"} on this server" console.log "Listening to #{domain}:#{port}" server.listen port, domain ~~~ ### 示例 Example Usage 使用[双向通信的客户端](http://island205.com/chapters/networking/bi-directional-client)。 Accessed by the [Bi-Directional Client](http://island205.com/chapters/networking/bi-directional-client): ~~~ $ coffee bi-directional-server.coffee Listening to localhost:9001 New connection from 127.0.0.1 127.0.0.1 sent: Ping 127.0.0.1 sent: Ping 127.0.0.1 sent: Ping [...] ~~~ ## 讨论 Discussion 大部分工作都在@socket.on ‘data’@这个处理器中，所有从客户端传过来的数据都在这里处理。一个真实的服务器会把数据传递给另外一个函数，对其进行处理，并产生响应供原始的处理器使用。 The bulk of the work lies in the @socket.on ‘data’@ handler, which processes all of the input from the client. A real server would likely pass the data onto another function to process it and generate any responses so that the original handler. 参看[双向的客户端](http://island205.com/chapters/networking/bi-directional-client), [最简单的客户端](http://island205.com/chapters/networking/basic-client), 以及[最简单的服务器](http://island205.com/chapters/networking/basic-server)这几个菜谱。 See also the [Bi-Directional Client](http://island205.com/chapters/networking/bi-directional-client), [Basic Client](http://island205.com/chapters/networking/basic-client), and [Basic Server](http://island205.com/chapters/networking/basic-server)recipes. ### 练习 Exercises * 添加自定义domain和端口的支持，可基于命令行参数，也可以使用配置文件。 * Add support for choosing the target domain and port based on command-line arguments or on a configuration file.