CSCI 460: Networks and Communications 1 | P a g e Project 1: File Transfer Protocol (FTP) Client Software Application Objectives 1. To learn how a computer network protocol is...

CSCI 460: Networks and Communications 1 | P a g e Project 1: File Transfer Protocol (FTP) Client Software Application Objectives 1. To learn how a computer network protocol is documented in a Request for Comments (RFC) by Internet Engineering Taskforce (IETF) as an Internet Standard. 2. To understand File Transfer Protocol (FTP) from RFC 959. 3. To learn and use Unix Network or Socket programming API. 4. To implement FTP Client software according to Internet Standard outlined in RFC 959. 5. To implement FPT Client software using C++ programming language and Unix Network or Socket programming API. Specifications You have been using File Transfer Protocol (FTP) to get or to store files from or to FTP servers. You use a FTP Client software in your host computer to communicate with an FTP server. FTP server runs a FTP Server software application. https://www.ietf.org/ https://tools.ietf.org/html/rfc959 https://beej.us/guide/bgnet/html/ http://www.linuxhowtos.org/C_C++/socket.htm https://tools.ietf.org/html/rfc959 https://beej.us/guide/bgnet/html/ http://www.linuxhowtos.org/C_C++/socket.htm CSCI 460: Networks and Communications 2 | P a g e In this project, you are going to implement your own FTP Client software application in C++ programming language using Unix Network or Socket programming API. FTP is a client-server protocol to transfer files to/from the servers. An FTP client sends FTP request messages to an FTP server. FTP server interprets the request message, takes appropriate action, and sends back response message to the client. RFC 959 describes FTP and its request and response messages in detail. You need to read and understand RFC 959 to complete this project. Although, RFC 959 describes many request messages, you need to implement only the followings: o USER o PASS o PWD o CWD o CDUP o PASV o NLST o RETR o QUIT Your FTP Client software must have a command-line user interface (UI) so that the users can enter commands through this interface. User commands of your application have different syntax than that of FTP request messages. User commands are more human readable. A user command has one or more corresponding FTP request message(s). Your software must accept and process following user commands.  help  user  pass  pwd  dir  cwd  cdup  get  quit Some of the user commands have an argument. For example, command user has an argument . A user command and its argument is always space separated. – Command ‘help’ displays the list of commands supported by this software application, their syntax, and meaning. https://beej.us/guide/bgnet/html/ http://www.linuxhowtos.org/C_C++/socket.htm CSCI 460: Networks and Communications 3 | P a g e – Command ‘user’ sends username to the FTP server for authentication. You need to support only one user with user name ‘csci460’ and password ‘460pass’. – Command ‘pass’ sends the password to the FTP server for authentication. – Command ‘pwd’ prints the current working directory of the FTP server. – Command ‘dir’ lists the contents of the current working directory of the FTP server. – Command ‘cwd’ changes the current working directory to another directory specified in the argument. If the specified directory is beyond current working directory of FTP server, an error is reported by the server. – Command ‘cdup’ changes the current working directory to its parent directory. If the parent directory is beyond server’s base directory, an error is reported by the server. – Command ‘get’ fetches the specified file from the current working directory of FTP server. If the specified file is not available an error is reported by the server. – Command ‘quit’ informs FTP server that the client application is quitting, so that the server can close the connection gracefully. It also closes the client connection gracefully and terminates the software. Your FTP client software application must interpret above user commands, translate them into appropriate FTP request messages, send the FTP request messages to FTP server, receive the response messages from the server, and present the response to the user in a user-friendly manner. CSCI 460: Networks and Communications 4 | P a g e FTP Client and Server communicate request and response messages over a control connection. FTP Server passively wait for a control connection and FTP Client actively open the control connection. Control Process Data transfer Process Control Process Data transfer Process 21 Control Process Data transfer Process Control Process Data transfer Process 62010 21 Passive Open By Server Active Open By Client Some requests/responses involve a data transmission. For example, RETR request involves a data transmission to transfer file content as the part of a successful response. FTP server uses a separate connection for each data transmission. A data connection is opened on demand and closed when a data transmission is complete. FTP server can operate either in active or in passive mode to open a data connection. In active mode, FTP server opens the data connection with the client on demand. At first, FTP Client choose an ephemeral port and opens a connection listener on this port. FTP Client sends this port number to the server using PORT request message and wait for the server to open the connection. After receiving the port number, FTP server opens the data connection. CSCI 460: Networks and Communications 5 | P a g e Control Process Data transfer Process Control Process Data transfer Process 62010 21 Control Process Data transfer Process Control Process Data transfer Process 62010 21 PORT 63000 63000 Control Process Data transfer Process Control Process Data transfer Process 62010 21 2063000 Passive Open By Client Active Open By Server PORT 63000 If the client is behind a firewall, FTP active mode fails to open a data connection. FTP passive mode has been proposed to solve this problem. In passive mode, when a data connection is required the server opens a connection listener so that client can send connection request to the listener and open a data connection. Client instructs the server to enter into passive mode by sending a PASV request message to the server. The server opens the connection listener on a port and sends the port number to the client in its PASV response. After receiving the PASV response, the client retrieves listener port number and sends a connection request to the listener port in order to open a data connection. CSCI 460: Networks and Communications 6 | P a g e In this project, you must implement passive mode and your FTP client software application, must send a PASV request before any data request, such as RETR and NLST. Tasks 1. You will work on and submit this project using GIT submission system of the department. A central repository named project1 has already been created for this project. 2. You are allowed to do this project alone or with another student. Your team has to be approved by your instructor before you proceed with your team work. If you are doing the project alone, create your own fork of project1 on the central GIT repository using following command. You should skip this step if you are doing the project in a team or group. ssh csci fork csci460/project1 csci460/$USER/project1 Control Process Data transfer Process Control Process Data transfer Process 62010 21 Control Process Data transfer Process Control Process Data transfer Process 62010 21 PASV 20 20 Control Process Data transfer Process Control Process Data transfer Process 62010 21 PASV 20 20 63000 Passive Open By Server Active Open By Client CSCI 460: Networks and Communications 7 | P a g e If you are working in a team, a forked repository for your team has already been created. For example, the central repository for team1 is csci460/team1/project1. In order to find out which team repository you have access to, type following command: ssh csci info 3. Create a folder named csci460 in your home folder and go into your csci460 folder. 4. Create a clone of your forked project1 repository using following command if you are working alone: git clone csci:csci460/$USER/project1 Create a clone of your forked team project1 repository using following command if you are working in a team (assuming you are working in team1, replace team1 with your own team): git clone csci:csci460/team1/project1 5. Repository project1 has been organized as follows: CSCI 460: Networks and Communications 8 | P a g e project1 bin build include resource src Makefile test README bin build include src example bin example bin 6. Continue your work in your cloned or local project1 repository and commit and push your work to your central project1 repository as it progresses. Instructor is expecting lots of incremental commits in the repository. Few number of commits is a red flag of academic misconduct. Instructor, will take further steps to verify the integrity of your work if there is any red flag of academic misconduct. 7. You will use supplied Makefile and Unix make utility to build, run, and test your application. You don’t need to and should not modify this Makefile. CSCI 460: Networks and Communications 9 | P a g e 8. A README template file has been supplied. You will need to complete README file to guide your user about your application. Complete your README file once you have completed your project. 9. Following header (*.h) files have been supplied in include folder in the repository. a. ftp_client_command.h b. ftp_client_connection.h c. ftp_client_session.h d. ftp_client_ui.h e. ftp_server_response.h You will need to implement the functions specified in the header files in corresponding source code files. For example, all functions in header file ‘ftp_client_command.h’ should be implemented in ‘ftp_client_command.cpp’ file. You are not allowed to change any header file. If you modify any header file, your project will be evaluated to zero. 10. All of your source code (cpp) files should be in src folder of the project. The source code of ftp_client.cpp file has been supplied, you don’t need to and should not change this code. Implement following cpp files in your src folder. a. ftp_client_command.cpp b. ftp_client_connection.cpp c. ftp_client_session.cpp d. ftp_client_ui.cpp 11. The lists of internal dependencies of the cpp files in this project are as follows. i. ftp_client.cpp: ftp_client_session.h, ftp_client_ui.h, ftp_client_command.h ii. ftp_client_ui.cpp: ftp_client_ui.h iii. ftp_client_connection.cpp: ftp_client_connection.h iv. ftp_client_sesion.cpp: ftp_client_session.h, ftp_client_connection.h, ftp_client_command.h, ftp_client_ui.h, ftp_server_response.h v. ftp_client_command.cpp: ftp_client_command.h, ftp_client_ui.h, ftp_client_connection.h, ftp_client_session.h, ftp_server_response.h 12. As mentioned earlier, you will build your FTP Client software application using build tool make. Build tool make will compile your source codes from src folder and save all object files in build folder. Build tool (make) will link all object files into a single executable and save the binary file (‘ftpclient’) of the application in bin folder. Build tool will also link CSCI 460: Networks and Communications 10 | P a g e necessary object files from test/build and build folders to create a test binary (ftpclienttest) in test/bin folder. 13. An example FTP Client Application binary (ftpclient) and an example FTP Server Application binary file (ftpserver) have been given in example/bin folder. An example FTP Client Test binary (ftpclienttest) has been given in test/example/bin folder. Make clean command will not delete these example binary files and don’t delete them yourself either. 14. Test code file named ftp_client_test.cpp has been placed in test/src folder. Your instructor has implemented all the functions prototyped in all the header files in test/include folder in the corresponding source code files in test/src folder and these source files are not exposed to you for technical reasons. You will not need to write these test codes either. Compiled object file (ftp_client_test.o and ftp_client_test_net_util.o) from your instructor’s test code have been supplied in test/build folder and build tool make will use this object file and other object files from your source code to create your test binary (ftpclienttest) in test/bin folder. Make clean command will not delete this test object file and don’t delete them yourself either. 15. To see how the example ftpclienttest works for deliverable1 enter following from your project root folder and observe console outputs. make test-example-deliverable1 These outputs will give you the idea about how many test cases your own code has to