实现一个代理服务器，用于代理HTTP请求以及FTP请求。
Overview
For this assignment, you must implement an Internet resource retriever to act
as a client and to make requests to a server, including the basic Web server
you have implemented. The basic Web server’s task is to deliver resources to
the client. The client requests a particular resource by writing an HTTP GET
(or similar) request. On receiving a legitimate request in the form of a URL
path, the server should return the contents of the corresponding file so that
the client can read the response from the server via the proxy server. When
networking facilities are available, the basic Web server (or any other
server) can be executed on one machine and the client can be executed on
another to make requests to the server. When networking facilities are not
available, both the basic Web server and the client may be executed on the
same machine. The client may refer to the server host by the standard name
localhost.
Requirements
Tutor-marked Exercise (TME) 1 requires that you develop three programs: one
for a client, one for a basic Web server, and one for a proxy server.
A proxy server is a special-purpose HTTP server; it is the core application
for this project. The proxy server has two socket connections. It “listens”
for communication from clients through one and launches requests to specific
Web servers through the other. In this exercise you should use a thread in the
proxy server so that it is able to send and receive messages simultaneously to
and from the server/client.
A basic Web server can deal with requests for resources from a client. It is
necessary to have a Web server return messages to a client such as 404 - not
found; 403 - bad request; etc., as appropriate. If the resource requested is
available, which means that the resource can be found on the disk of the Web
server, the Web server needs to read the resource and write the data to the
socket. For example, a Web server may find an HTML file or a JPEG (image) file
on its disk and transfer the data to the socket.
The client basically needs access to the function that allows the user to
input the resource URL that identifies the resource s/he wants to access.
However, the client has to access the resource by sending a request to the
proxy server, and then the client must receive the resource from the proxy
server. No matter what kind of data the client receives, the client only needs
to print it on the screen. Note that where the response from a server is an
HTML file, a typical Web browser will render it according to HTML semantics.
This functionality is not considered in this exercise.
Note: Your tutor may use resource URLs other than those for the basic Web
server (e.g., Java tutorial Web pages and public FTP files).
To test your basic Web server’s function you can simply use an HTML file named
testfile.html and a JPG file name testfile.jpg with Microsoft Internet
Explorer or Mozilla Firefox. After you are completely certain that your basic
Web server works properly, you can use http://127.0.0.1/testfile.html
or http://localhost/testfile.jpg
with your client to test whether your proxy
works. Finally, try to use http://www.google.com
or ftp://ftp.us.dell.com/readme.txt within your client to test whether your
proxy works properly.
Deliverables
Your assignment must be zipped into one file and uploaded using the Assignment
Drop Box feature of Moodle. The file must include
- all source files.
- a complete test plan.
Before you submit your TME, please review Tutor-marked Exercise Requirements
for full details of TME requirements and to review the marking scheme. Please
contact your tutor if you have any questions.
Note: Your tutor will not accept TMEs by email.
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