Adapted from Kurose & Ross - Computer Networking: a top-down approach featuring the InternetCBOK categories: Abstraction, Design, Data & Information, Networking, ProgrammingIn this practical, you will learn how web proxy servers work and one of their basic functionalities - caching.TaskYour task is to develop a small web proxy server which is able to cache web pages.It is a very simple proxy server which only understands simple HTTP/1.1 GET-requests but is able to handle all kinds of objects - not just HTML pages, but also images.IntroductionIn this practical, you will learn how web proxy servers work and one of their basic functionalities, caching (Links to an external site.)Links to an external site.. Generally, when a client (e.g. your browser) makes a web request the following occurs:1.The client sends a request to the web server2.The web server then processes the request3.The web server sends back a response message to the requesting clientAnd lets say that the entire transaction takes 500 ms.In order to improve the performance, we create a proxy server between the client and the web server. The proxy server will act as a middle-man for the web transactions. Requesting a web request will now occur in the following steps:1.The client sends a request to the proxy server2.Skip to step 7 If the proxy server has cached the response3.Forward the request to the web server4.The web server processes the request5.The web server sends a response back to the proxy server6.The proxy server caches the response7.The proxy server returns the cached response to the clientOn the first request, the transaction may be a fraction longer than the previous example. However, subsequent requests will be significantly faster due to reduced network latency and server load (sometimes less than 10 ms).The mechanism for caching can be as simple as storing a copy of a resource on the proxy servers file system.Steps for approaching the practicalStep 1Understand the HTTP/1.1 requests/responses of the proxy. Your proxy MUST be able to handle GET requests from a client. Your proxy may handle other request types (such as POST) but this is not required.You need to know the following:1.What HTTP request will the browser send to the proxy?2.What will HTTP response look like?3.In what ways will the response look different if it comes from the proxy than if it comes from the origin server (i.e. the server where the original page is stored?). You will not be able to test this yet, but what do you think would happen?Step 2Understand the socket connections:1.How will the client know to talk to the proxy?2.What host and port number will the proxy be on?3.The proxy may need to connect to the origin server (if the web object is not in the cache), what host and port number will the proxy connect to?4.Where will the proxy get the web object information?Step 3: CheckpointMake sure you have the answers to steps 1 & 2 before you go any further.You cant code it if you dont know what should happen.Ask questions on the discussions forum if you are unsure above the above.Step 4: Python CodeNow that you know what should be happening, have a look at the code?here.Look at the interactions you identified in steps 1 & 2 and see where they would occur in the code.Review the python code presented in the sockets lecture. Youll find details of the socket calls in the Python Socket library documentation?https://docs.python.org/2.7/library/socket.html?(Links to an external site.)Links to an external site.(Links to an external site.)Links to an external site.You wont just be able to copy the lecture code, but it shows you the key steps; creating sockets, connecting sockets, sending data on sockets and receiving data on sockets.Your task is to make the correct socket calls and supply the correct arguments for those calls.You will only need to fill in the code between the comment lines.# ~~~~ INSERT CODE ~~~~...# ~~~~ END CODE INSERT ~~~~The comments above the comments lines give you hints to the code to insert.Step 5: Differences in Python and CIf you are new to python, look at the code structure. Most of the code is given to you with your focus just on adding the networking code. A couple of things that are different in Python than in the C derived languages:1.Python uses whitespace to indicate code blocks and end of lines. Note there are no brackets or braces?{ }?around code blocks and no semi-colons;at the end of lines. The indentation isnt just important for readability in Python, it affects how your code runs. Make sure you indent code blocks correctly.2.Python has a tuple data structure. So functions can return more than one value, or more precisely return one tuple with multiple values, but the syntax allows the parenthesis to be left off. Tuples appear in the lecture slides in the line:clientSocket.connect((serverName,serverPort))?(serverName, serverPort) is a tuple of two values that are passed as the argument to the connect()function.connectionSocket, addr= serverSocket.accept()The accept() call returns a tuple of two values, the first value is the new socket and the second is the address information. This is the same as:(connectionSocket, addr)= serverSocket.accept()The use of the?( )?around the tuple is optional.Step 6Start with getting the proxy working when a cached file is requested. Where it will return the response itself and does not have to contact the origin serverStep 7Once that is working, add the code to handle the case where the file is not cached by the proxy and the proxy must request it from the origin server.Step 8In both steps 6 & 7, make use of both telnet utility and a browser to test your proxy server. You can also use Wireshark to capture what is being sent/received from the origin server.Running your proxy in the labs and WebsubThe labs and test machines are running Python 2.7. Make sure that your submission is compatible with Python 2 and does not use Python 3 features that are not backward compatible with Python 2.7.The University proxy will intercept any attempt to connect to a host outside of the University and require authentication (which is outside the scope of this practical), thus, your proxy will not be able to connect to origin servers outside of the University when running on computers inside the University. When testing inside the University, use URLs within the University infrastructure. This should not affect you when running your proxy outside the University.Running the Proxy ServerDownload the template file and save it as Proxy.py.Run the following command in terminal to run the proxy server$ python Proxy.py localhost 8888You can change localhost to listen on another IP address for requests, localhost is the address for your machine.You can change 8888 as the port to listen to.When you run the proxy server for the first time, it will loop forever failing to connect to a server. Thats ok for now. Press Ctrl+C to terminal the program.When you are ready to test your proxy server, open a Web browser and navigate to http://localhost:8888/https://ecms.adelaide.edu.auNote that when typing the proxy into the browser request in this way, the browser may only display the main page and may fail to download associated files such as images and style sheets. This is due to a difference in URI requirements when sending requests to a proxy vs sending to an origin Web server (well look at this in the tutorials).Configuring your Browser (optional)You can also directly configure your web browser to use your proxy if you want without using the URI. This depends on your browser.In Internet Explorer, you can set the proxy in Tools > Internet Options > Connections tab > LAN Settings.In Netscape (and derived browsers such as Mozilla), you can set the proxy in?Tools > Options > Advanced tab > Network tab > Connection Settings.In both cases, you need to give the address of the proxy and the port number that you set when you ran the proxy server. You should be able to run the proxy and the browser on the same computer without any problem. With this approach, to get a web page using the proxy server, you simply provide the URL of the page you want.For example, running https://ecms.adelaide.edu.au would be the same as running http://localhost:8888/https://ecms.adelaide.edu.auSet up like this, the browser should successfully load both the main web page and all associated files due to reasons well discuss in tutorials.Testing your codeWhen it comes time to test your code, cUrl is a useful tool to use.Lets have a look at these two tests:Obtained remote file$ curl -sI localhost:8080/https://ecms.adelaide.edu.au | head -n 1HTTP/1.1 200 OKThe above command requests https://ecms.adelaide.edu.au via the Web proxy.-I prints out response headers and -s removes additional output and head -n 1 extracts the first line from the cUrl command.The result is the first line in the response from the proxy. This response should match if you were talking directly to the origin server, like so$ curl -sI https://ecms.adelaide.edu.au | head -n 1HTTP/1.1 200 OKHandle page that does not exist$ curl -sI localhost:8080/https://ecms.adelaide.edu.au/fakefile.html | head -n 1HTTP/1.1 404 Not FoundThe response for a path that doesnt exist shows the above status code. Your proxy to work correctly will also need to handle this case too.SubmissionYour proxy server will be inside the Proxy.py file only.Your work will need to be submitted to?Websub?with the assignment path?/2019/s1/cna/webproxyThe Web submission system will perform a static analysis of your code. Your code will be run by one of the teachers.Prac 1: Web ProxyPrac 1: Web ProxyCriteria Ratings PtsThis criterion is linked to a Learning OutcomeProxy server started 0.0 ptsFull Marks 0.0 ptsNo Marks 0.0 ptsThis criterion is linked to a Learning OutcomeConnected to Proxy server 10.0 ptsFull Marks 0.0 ptsNo Marks 10.0 ptsThis criterion is linked to a Learning OutcomeObtained remote homepage 2.0 ptsFull Marks 0.0 ptsNo Marks 2.0 ptsThis criterion is linked to a Learning OutcomeObtained remote file 2.0 ptsFull Marks 0.0 ptsNo Marks 2.0 ptsThis criterion is linked to a Learning OutcomeHandle page that does not exist 2.0 ptsFull Marks 0.0 ptsNo Marks 2.0 ptsThis criterion is linked to a Learning OutcomeCache requested webpages 2.0 ptsFull Marks 0.0 ptsNo Marks 2.0 ptsThis criterion is linked to a Learning OutcomeRead from a cached file 1.0 ptsFull Marks 0.0 ptsNo Marks 1.0 ptsThis criterion is linked to a Learning OutcomeRedownloaded the file from server after file was removed 1.0 ptsFull Marks 0.0 ptsNo Marks 1.0 ptsThis criterion is linked to a Learning OutcomeHandles internal server error 4.0 ptsFull Marks 0.0 ptsNo Marks 4.0 ptsTotal Points: 24.0本团队核心人员组成主要包括硅谷工程师、BAT一线工程师，精通德英语！我们主要业务范围是代做编程大作业、课程设计等等。我们的方向领域：window编程 数值算法 AI人工智能 金融统计 计量分析 大数据 网络编程 WEB编程 通讯编程 游戏编程多媒体linux 外挂编程 程序API图像处理 嵌入式/单片机 数据库编程 控制台 进程与线程 网络安全 汇编语言 硬件编程 软件设计 工程标准规等。其中代写编程、代写程序、代写留学生程序作业语言或工具包括但不限于以下范围:C/C++/C#代写Java代写IT代写Python代写辅导编程作业Matlab代写Haskell代写Processing代写Linux环境搭建Rust代写Data Structure Assginment 数据结构代写MIPS代写Machine Learning 作业 代写Oracle/SQL/PostgreSQL/Pig 数据库代写/代做/辅导Web开发、网站开发、网站作业ASP.NET网站开发Finance Insurace Statistics统计、回归、迭代Prolog代写Computer Computational method代做因为专业，所以值得信赖。如有需要，请加QQ：99515681 或邮箱：[email protected] 微信：codehelp
