Shulou(Shulou.com)06/02 Report--

In this issue, the editor will bring you about how to use twisted to achieve TCP communication in python. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

0. Write at the front

Both the server and the client are started through twisted's reactor, so you need to import the reactor module under the twisted.internet package first.

From the source code of the reactor module, we can see that the reactor module is actually composed of multiple interfaces, and it is suggested that the specific content needs to see the specific comments of each interface in the interfaces module under the twisted.internet package.

Of course, the comments of the reactor module also show that twisted can not only be used for TCP services, but also provide network API, threading, scheduling and other functions, but this experiment only tests the server side and client side of TCP.

The supported interfaces mentioned in the reactor comments are: @ see: l {IReactorCore} @ see: l {IReactorTime} @ see: l {IReactorProcess} @ see: l {IReactorTCP} @ see: l {IReactorSSL} @ see: l {IReactorUDP} @ see: l {IReactorMulticast} @ see: l {IReactorUNIX} @ see: l {IReactorUNIXDatagram} @ see: l {IReactorFDSet} @ see: l {IReactorThreads} @ see: l {IReactorPluggableResolver} 1.TCP server-side reactor reactor.

According to the comments of the reactor module above, it is found that the TCP-related IReactorTCP interface under the interfaces module needs to be viewed, so let's move to the IReactorTCP interface.

There are two methods in the IReactorTCP interface, listenTCP and connectTCP. No matter from the method name or its description, we can see that the former is listening to a port to provide TCP services, and the latter is a TCP client connected to the server.

Def listenTCP (port, factory, backlog=50, interface=''): def connectTCP (host, port, factory, timeout=30, bindAddress=None):

So to open a TCP server, we need to use the listenTCP method, which has four parameters

The meaning of the parameter name defaults to the port that port listens to, that is, the port started by the TCP service-the factory class of the factory service side (as indicated in the note: see the ServerFactory class in the protocol module under the twisted.internet package for details)-the backlog listening queue, the local IPv4 or IPv6 address to which the response thread 50interface is bound, which defaults to the empty address of all IPv4''Factory factory class.

After setting the first two parameters, you can start the TCP service with the following two lines of code

Reactor.listenTCP (port, ServerFactory ()) reactor.run ()

However, there is a problem with the service started at this time, and an error will be reported when a client connects to the service

-File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ tcp.py", line 1427, in doRead self._buildAddr (addr)) File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ protocol.py", line 140, in buildProtocol p = self.protocol () builtins.TypeError: 'NoneType' object is not callable

According to the error prompt, we found the cause of the problem:

When the client connects to the server, the buildProtocol method in the Factory class (the parent class of ServerFactory) is called to establish the communication protocol (here it can be understood as the implementation method of reading and writing between the client and the server). The method pointed to by self.protocol needs to be called to initialize the protocol.

However, at this time, the protocol is None, so there is an error in the initialization phase of the protocol.

Protocol protocol class

Taking a look at the Factory class in the protocol module again, it is found that the class method forProtocol is used to create an factory instance, but a protocol instance is required.

Well, our goal is one step closer, so let's move on to the Protocol class.

Also in the protocol module, we find the Protocol class, which inherits from the BaseProtocol class, with a total of the following methods

BaseProtocol.makeConnection: used to open a connection. The connectionMade method will be called back when the connection is opened.

BaseProtocol.connectionMade: not implemented. Call back the method when the connection is successful

Protocol.logPrefix: returns the class name of the current class, used for log

Protocol.dataReceived: not implemented. The method that is called when a request is received

Protocol.connectionLost: not implemented. The method called when the connection is disconnected

So now we just need to inherit the Protocol class, write our own implementation protocol, and only need to implement the three methods that are not implemented in the parent class.

For simplicity, we only record the connection information of the client and output the log in the connectionMade and connectionLost methods, while in the dataReceived method we print out the information received and return a message to the client after 5 seconds

Class TcpServer (Protocol):: CLIENT_MAP = {} # to save the connection information of the client def connectionMade (self): addr = self.transport.client # get the connection information of the client print ("connected", self.transport.socket) TcpServer.CLIENT_ map [addr] = self def connectionLost (self Reason): addr = self.transport.client # get client connection information if addr in TcpServer.CLIENT_MAP: print (addr, "Lost Connection from TcpServer", 'Reason:', reason) del TcpServer.CLIENT_ map [addr] def dataReceived (self Tcp_data): addr = self.transport.client # get the connection information of the client nowTime = datetime.datetime.now (). Strftime ('% Y-%m-%d% HV% MV% S') try: msg = tcp_data.decode ("utf-8") print ("Received msg", msg, "from Tcp Client") Addr) time.sleep (5) str = "response from the server" + nowTime self.transport.write (str.encode ("utf-8")) except BaseException ase: print ("Comd Execute Error from", addr, "data:" Tcp_data) str = "server exception" + nowTime self.transport.write (str.encode ("utf-8")) starts the TCP service

Well, the Protocol class has been implemented, and we use it to create a factory instance and start the TCP service

Port = 9527 serverFactory = Factory.forProtocol (TcpServer) reactor.listenTCP (port, serverFactory) print ("#", "Starting TCP Server on", port, "#") reactor.run ()

The TCP service started successfully and no error was reported after the client connected

D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ python.exe D:/MyWorkSpaces/projects/all/sample/python/twisted/server.py# Starting TCP Server on 9527 # connected Received msg Hello server, I am the client 2019-08-10 11:13:09 from Tcp Client ('127.0.0.1 2.TCP client reactor reactor)

With the server experience, let's look back at the connectTCP method in the IReactorTCP interface of the reactor module, which has a total of five parameters

The meaning of the parameter name defaults to host server address, IPv4 or IPv6-prot server port-factory class of factory client (as prompted in the note: see ClientFactory class in protocol module under twisted.internet package for details)-timeout connection timeout, local address in unit s30bindAddress, meta-ancestor None in (host,port) format

It is also very simple, we only need the following two lines of code to start the client, but similar to the server, we also need to implement an instance of the Factory factory class and the Protocol protocol class before that.

Reactor.connectTCP (host, port, factory) reactor.run () Factory factory class

According to the annotation of the connectTCP method, we can find the ClientFactory class directly, and there are three methods in the class that need to be implemented.

ClientFactory.startedConnecting: not implemented. This method is called when the connection is opened

ClientFactory.clientConnectionFailed: not implemented. This method is called when the connection fails

ClientFactory.clientConnectionLost: not implemented. This method is called when the connection is disconnected

Similarly, for simplicity, we only record the log log in the startedConnecting method, and retry the connection after 30 seconds after entering the log in the clientConnectionFailed and clientConnectionLost methods

Class TcpClientFactory (ClientFactory): def startedConnecting (self, connector): print ("Starting Connecting To Tcp Server", (connector.host, connector.port)) def clientConnectionLost (self, connector, reason): print ("Lost Connection from Tcp Server", (connector.host, connector.port), 'Reason:', reason) time.sleep (30) connector.connect () def clientConnectionFailed (self, connector, reason): print ("Failed To Connect To Tcp Server" (connector.host, connector.port), 'Reason:', reason) time.sleep (30) connector.connect ()

When we start the TCP client, we find the same error as when we first started the server. This time we have experience because the implementation of the Protocol class is missing.

-File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ selectreactor.py", line 149, in _ doReadOrWrite why = getattr (selectable, method) () File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ tcp.py", line 627, in doConnect self._connectDone () File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ tf2\ lib\ lib\ site-packages" In _ connectDone self.protocol = self.connector.buildProtocol (self.getPeer ()) File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ base.py", line 1157, in buildProtocol return self.factory.buildProtocol (addr) File "D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ lib\ site-packages\ twisted\ internet\ protocol.py", line 140, in buildProtocol p = self.protocol () builtins.TypeError: 'NoneType' object is not callable Protocol protocol class

We use the same Protocol parent class as the server side. Here we do something slightly different from the server side. When implementing the connectionMade method, we send a message to the server side.

Class TcpClient (Protocol): SERVER_MAP = {} def connectionMade (self): addr = self.transport.addr # get server-side connection information print ("connected" Self.transport.socket) client_ip = addr [0] TcpClient.SERVER_ map [client _ ip] = self nowTime = datetime.datetime.now (). Strftime ('% Y-%m-%d% HV% MRV% S') str = "Hello server" I am the client "+ nowTime self.transport.write (str.encode (" utf-8 ")) # send the message def connectionLost (self, reason): addr = self.transport.addr # get the connection information of the server client_ip = addr [0] if client_ip in TcpClient.SERVER_MAP: del TcpClient.SERVER_ map [client _ ip] def dataReceived (self Tcp_data): addr = self.transport.addr # get the connection information on the server side nowTime = datetime.datetime.now (). Strftime ('% Y-%m-%d% HV% MV% S') try: msg = tcp_data.decode ("utf-8") print ("Received msg", msg, "from Tcp Server") Addr) time.sleep (5) str = "response from the client" + nowTime self.transport.write (str.encode ("utf-8")) except BaseException ase: print ("Comd Execute Error from", addr, "data:" Tcp_data) str = "client exception" + nowTime self.transport.write (str.encode ("utf-8")) starts the TCP client

Because the creation of the Factory class is somewhat different from that on the server side, we instantiated the factory object through the Factory.forProtocol method on the server side, while on the client side, we inherited the subclass ClientFactory of the Factory class, so we need to override the buildProtocol method to set the protocol instance

Override the buildProtocol method in the TcpClientFactory class:

Class TcpClientFactory (ClientFactory): def buildProtocol (self, addr): print ("Connected To Tcp Server", addr) self.protocol = TcpClient () return self.protocol

Then start the TCP client with the following code:

Host = "127.0.0.1" port = 9527 reactor.connectTCP (host, port, TcpClientFactory ()) reactor.run ()

The TCP client started successfully and no error was reported after connecting to the server

D:\ MyWorkSpaces\ tools\ Anaconda3\ envs\ tf2\ python.exe D:/MyWorkSpaces/projects/all/sample/python/twisted/client.pyStarting Connecting To Tcp Server ('127.0.0.1, 9527) Connected To Tcp Server IPv4Address (type='TCP', host='127.0.0.1', port=9527) connected Received msg response from the server 2019-08-10 11:57:42 from Tcp Server (' 127.0.0.1' 9527) the above is how to use twisted to achieve TCP communication in python shared by the editor. If you happen to have similar doubts, you might as well refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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