Quick Guide to Python Socket Programming 吳俊興 國立高雄大學資訊工程學系

Transcription

1 Quick Guide to Python Socket Programming 吳俊興 國立高雄大學資訊工程學系

2 Python Overview Philosophy - code readability Uses whitespace indentation Rather than curly braces or keywords, to delimit blocks Can express concepts in fewer lines of code Built-in support for arbitrary precision arithmetic (long, Decimal, Fractional, ) General-purpose, high-level programming language Interpreters Time-critical functions to extension modules written in languages such as C Pyinstaller to package into stand-alone executable programs Cython to translate a Python script into C APIs available in C/C++ to extend and embed the Python Interpreter Multiple programming paradigms Object-oriented, imperative (statements to change program's states) and functional programming or procedural styles Features A dynamic type system An automatic memory management A large and comprehensive standard library 2

3 Download Python Releases for Windows Python 3.7.0a2 ( ) Python ( ) Change Windows console/filesystem encoding to UTF-8 Python ( ) Windows x86-64 executable installer Windows x86 executable installer Python 3.0 ( ) Compatible to Python 2.6 and 2.7 (not to 2.0) print("hello, world!") # for 2.6 or later print "Hello, world! # for versions earlier than 2.6 raw_input() changed to input() Unicode text (str) v.s. data (bytes, b"...") - must always explicitly convert str.encode() to go from str to bytes, and bytes.decode() to go from bytes to str Supports Unicode characters in identifiers 3

4 Install 4

5 Customize Installation 5

6 Python IDLE Integrated Development and Learning Environment coded in 100% pure Python, using the tkinter GUI toolkit cross-platform: works mostly the same on Windows, Unix, and Mac OS X Python shell window (interactive interpreter) with colorizing of code input, output, and error messages multi-window text editor with multiple undo, Python colorizing, smart indent, call tips, auto completion, and other features search within any window, replace within editor windows, and search through multiple files (grep) debugger with persistent breakpoints, stepping, and viewing of global and local namespaces configuration, browsers, and other dialogs Ctrl-D or exit() to quit 6

7 Your 1 st Python under IDLE Write simple code under Python shell >>> print("hello, I'm A from NUK CSIE.") Invoke Editor Window to develop codes and Run File New File Run Run Module (F5) (Save as hello.py) 7

8 Tips for Python Under Windows Default Windows encoding issue Auto-close issue 8

9 Quick Python Script Explanation for Programmers 9

10 Socket Programming Goal: learn how to build client/server applications that communicate using sockets Socket: door between application process and endend-transport protocol application process socket application process controlled by app developer transport transport network link Internet network link controlled by OS physical physical 10

11 Socket Types Two socket types for two transport services: UDP: unreliable datagram TCP: reliable, byte stream-oriented Application Example: 1. Client reads a line of characters (data) from its keyboard and sends the data to the server 2. The server receives the data and converts characters to uppercase 3. The server sends the modified data to the client 4. The client receives the modified data and displays the line on its screen 11

12 Socket programming with UDP UDP: no connection between client & server no handshaking before sending data sender explicitly attaches IP destination address and port # to each packet receiver extracts sender IP address and port# from received packet UDP: transmitted data may be lost or received out-of-order Application viewpoint: UDP provides unreliable transfer of groups of bytes ( datagrams ) between client and server 2-12

13 Client/Server Socket Interaction: UDP server (running on serverip) create socket, port= x: serversocket = socket(af_inet,sock_dgram) read datagram from serversocket write reply to serversocket specifying client address, port number client create socket: clientsocket = socket(af_inet,sock_dgram) Create datagram with server IP and port=x; send datagram via clientsocket read datagram from clientsocket close clientsocket 13

14 Example App: UDP Client include Python s socket library create UDP socket for server get user keyboard input Attach server name, port to message; send into socket Python UDPClient from socket import * servername = hostname serverport = clientsocket = socket(af_inet, SOCK_DGRAM) message = raw_input( Input lowercase sentence: ) clientsocket.sendto(message.encode(), read reply characters from socket into string print out received string and close socket (servername, serverport)) modifiedmessage, serveraddress = clientsocket.recvfrom(2048) print(modifiedmessage.decode()) clientsocket.close() 2-14

15 Example App: UDP Server create UDP socket bind socket to local port number loop forever Read from UDP socket into message, getting client s address (client IP and port) send upper case string back to this client Python UDPServer from socket import * serverport = serversocket = socket(af_inet, SOCK_DGRAM) serversocket.bind(('', serverport)) print ( The server is ready to receive ) while True: message, clientaddress = serversocket.recvfrom(2048) modifiedmessage = message.decode().upper() serversocket.sendto(modifiedmessage.encode(), clientaddress) 2-15

16 Socket Programming with TCP client must contact server server process must first be running server must have created socket (door) that welcomes client s contact client contacts server by: Creating TCP socket, specifying IP address, port number of server process when client creates socket: client TCP establishes connection to server TCP when contacted by client, server TCP creates new socket for server process to communicate with that particular client allows server to talk with multiple clients source port numbers used to distinguish clients (more in Chap 3) application viewpoint: TCP provides reliable, in-order byte-stream transfer ( pipe ) between client and server 16

17 Client/Server Socket Interaction: TCP server (running on hostid) create socket, port=x, for incoming request: serversocket = socket() client wait for incoming connection request connectionsocket = serversocket.accept() read request from connectionsocket write reply to connectionsocket close connectionsocket TCP connection setup create socket, connect to hostid, port=x clientsocket = socket() send request using clientsocket read reply from clientsocket close clientsocket 17

18 Example App: TCP Client Python TCPClient create TCP socket for server, remote port No need to attach server name, port from socket import * servername = servername serverport = clientsocket = socket(af_inet, SOCK_STREAM) clientsocket.connect((servername,serverport)) sentence = input( Input lowercase sentence: ) clientsocket.send(sentence.encode()) modifiedsentence = clientsocket.recv(1024) print ( From Server:, modifiedsentence.decode()) clientsocket.close() 2-18

19 Example App: TCP Server create TCP welcoming socket server begins listening for incoming TCP requests loop forever server waits on accept() for incoming requests, new socket created on return read bytes from socket (but not address as in UDP) close connection to this client (but not welcoming socket) Python TCPServer from socket import * serverport = serversocket = socket(af_inet,sock_stream) serversocket.bind((,serverport)) serversocket.listen(1) print The server is ready to receive while True: connectionsocket, addr = serversocket.accept() sentence = connectionsocket.recv(1024).decode() capitalizedsentence = sentence.upper() connectionsocket.send(capitalizedsentence. encode()) connectionsocket.close() 2-19

20 Example: TCPClient.py and TCPServer.py TCPClient.py TCPServer.py Python 3.6 print() instead of print input() instead of raw_input() Explicitly sentence.encode() and modifiedsentence.decode() Change servername and serverport if required 20

21 Demo: TCPClient and TCPServer Start TCPServer.py in DOS Prompt > python TCPServer.py Use telnet localhost to test if it is running Press Ctrl-C to interrupt > Also OK to start from IDLE Start TCPClient.py from Python IDLE File Open: TCPClient.py Run Run Module (F5) Input: Hello, I'm A from Kaohsiung. 21

22 Python Documents The Python Tutorial The Python Language Reference The Python Standard Library PyPI - the Python Package Index 122,139 packages ( ) Introduction 2. Built-in Functions 3. Built-in Constants 4. Built-in Types 5. Built-in Exceptions 6. Text Processing Services 7. Binary Data Services 8. Data Types 9. Numeric and Mathematical Modules 10. Functional Programming Modules 11. File and Directory Access 12. Data Persistence 13. Data Compression and Archiving 14. File Formats 15. Cryptographic Services 16. Generic Operating System Services 17. Concurrent Execution 18. Interprocess Communication and Networking 19. Internet Data Handling 20. Structured Markup Processing Tools 21. Internet Protocols and Support 22. Multimedia Services 23. Internationalization 24. Program Frameworks 25. Graphical User Interfaces with Tk 26. Development Tools 27. Debugging and Profiling 28. Software Packaging and Distribution 29. Python Runtime Services 30. Custom Python Interpreters 31. Importing Modules 32. Python Language Services 33. Miscellaneous Services 34. MS Windows Specific Services 35. Unix Specific Services 36. Superseded Modules 37. Undocumented Modules 22

23 Standard Library (Internet Related) 21. Internet Protocols and Support webbrowser Convenient Web-browser controller cgi Common Gateway Interface support cgitb Traceback manager for CGI scripts wsgiref WSGI Utilities and Reference Implementation urllib URL handling modules urllib.request Extensible library for opening URLs urllib.response Response classes used by urllib urllib.parse Parse URLs into components urllib.error Exception classes raised by urllib.request urllib.robotparser Parser for robots.txt http HTTP modules http.client HTTP protocol client ftplib FTP protocol client poplib POP3 protocol client imaplib IMAP4 protocol client nntplib NNTP protocol client smtplib SMTP protocol client smtpd SMTP Server telnetlib Telnet client uuid UUID objects according to RFC socketserver A framework for network servers http.server HTTP servers http.cookies HTTP state management http.cookiejar Cookie handling for HTTP clients xmlrpc XMLRPC server and client modules xmlrpc.client XML-RPC client access xmlrpc.server Basic XML-RPC servers ipaddress IPv4/IPv6 manipulation library 18. Interprocess Communication and Networking socket Low-level networking interface ssl TLS/SSL wrapper for socket objects select Waiting for I/O completion selectors High-level I/O multiplexing asyncio Asynchronous I/O, event loop, coroutines and tasks asyncore Asynchronous socket handler asynchat Asynchronous socket command/response handler signal Set handlers for asynchronous events mmap Memory-mapped file support 19. Internet Data Handling An and MIME handling package json JSON encoder and decoder mailcap Mailcap file handling mailbox Manipulate mailboxes in various formats mimetypes Map filenames to MIME types base64 Base16, Base32, Base64, Base85 Data Encodings binhex Encode and decode binhex4 files binascii Convert between binary and ASCII quopri Encode and decode MIME quoted-printable data uu Encode and decode uuencode files 20. Structured Markup Processing Tools html HyperText Markup Language support html.parser Simple HTML and XHTML parser html.entities Definitions of HTML general entities XML Processing Modules xml.etree.elementtree The ElementTree XML API xml.dom The Document Object Model API xml.dom.minidom Minimal DOM implementation xml.dom.pulldom Support for building partial DOM trees xml.sax Support for SAX2 parsers xml.sax.handler Base classes for SAX handlers xml.sax.saxutils SAX Utilities xml.sax.xmlreader Interface for XML parsers xml.parsers.expat Fast XML parsing using Expat 23

24 Chinese String: big5 v.s. UTF-8 Encodings Specify the right coding Python default is utf-8, but not in all editors (big5 in Windows NotePad) 24