Tornado demo3 - tcpecho分析

在这个demo中，主要是使用了Tornado中异步的TCP client和server来实现一个简单的echo效果（即客户端发送的message会从server端返回到client）。代码的github链接点这里。

1 Server端代码分析

 import logging
 from tornado.ioloop import IOLoop
 from tornado import gen
 from tornado.iostream import StreamClosedError
 from tornado.tcpserver import TCPServer
 from tornado.options import options, define

 define("port", default=9888, help="TCP port to listen on")
 logger = logging.getLogger(__name__)

 class EchoServer(TCPServer):
     @gen.coroutine
     def handle_stream(self, stream, address):
         while True:
             try:
                 data = yield stream.read_until(b"\n")
                 logger.info("Received bytes: %s", data)
                 if not data.endswith(b"\n"):
                     data = data + b"\n"
                 yield stream.write(data)
             except StreamClosedError:
                 logger.warning("Lost client at host %s", address[0])
                 break
             except Exception as e:
                 print(e)

 if __name__ == "__main__":
     options.parse_command_line()
     server = EchoServer()
     server.listen(options.port)
     logger.info("Listening on TCP port %d", options.port)
     IOLoop.current().start()

server.py

涉及到引入的模块及作用：

import logging   //用来记录日志
from tornado.ioloop import IOLoop
from tornado import gen    //实现异步
from tornado.iostream import StreamClosedError   //处理iostream
from tornado.tcpserver import TCPServer   // 非阻塞单线程的TCP server及其相关哦功能
from tornado.options import options, define  // options参数相关

server端代码并不复杂，首先定义了默认的监听端口，并且生成了一个logger实例。（logging用法点这里。）

define("port", default=9888, help="TCP port to listen on")
logger = logging.getLogger(__name__)

然后创建EchoServer类如下。这个类继承TCPServer(更多参考)。里面重写了handle_stream方法。handle_stream接收了stream和address两个参数，stream是一个iostream的object，address是client端地址。逻辑比较清晰，使用try, except来捕获io错误，如果没有错误的话，会读取stream内容直到遇到换行停止。读取到的data会写回到client端，通过write(data)。

handle_stream方法是用了@gen.coroutine装饰器和yield来实现异步读取\写回iostream。

class EchoServer(TCPServer):
    @gen.coroutine
    def handle_stream(self, stream, address):
        while True:
            try:
                data = yield stream.read_until(b"\n")
                logger.info("Received bytes: %s", data)
                if not data.endswith(b"\n"):
                    data = data + b"\n"
                yield stream.write(data)
            except StreamClosedError:
                logger.warning("Lost client at host %s", address[0])
                break
            except Exception as e:
                print(e)

最后在main部分，生成一个EchoServer实例并监听定义的端口，然后启动事件的ioloop。

options.parse_command_line()
server = EchoServer()
server.listen(options.port)
logger.info("Listening on TCP port %d", options.port)
IOLoop.current().start()

2 Client端代码分析

 from __future__ import print_function
 from tornado.ioloop import IOLoop
 from tornado import gen
 from tornado.tcpclient import TCPClient
 from tornado.options import options, define

 define("host", default="localhost", help="TCP server host")
 define("port", default=9888, help="TCP port to connect to")
 define("message", default="ping", help="Message to send")

 @gen.coroutine
 def send_message():
     stream = yield TCPClient().connect(options.host, options.port)
     yield stream.write((options.message + "\n").encode())
     print("Sent to server:", options.message)
     reply = yield stream.read_until(b"\n")
     print("Response from server:", reply.decode().strip())

 if __name__ == "__main__":
     options.parse_command_line()
     IOLoop.current().run_sync(send_message)

client.py

client 端首先定义了3个option, host,port,以及message，分别为要连接的服务端的host ip, 端口和要发送的message.

send_message用来向server端发送和接收数据。同样这里使用@gen.coroutine和yield来实现异步。

@gen.coroutine
def send_message():
    stream = yield TCPClient().connect(options.host, options.port)
    yield stream.write((options.message + "\n").encode())
    print("Sent to server:", options.message)
    reply = yield stream.read_until(b"\n")
    print("Response from server:", reply.decode().strip())

3 运行效果

server端运行后，可以使用运行client.py发送消息，发送完成后连接会端口。也可以使用telnet保持连接，交互式的发送数据给server端。