Implementation of FTP in C++
I. Implementation Outline :
- 'C++' language was used to implement both the client and the server.
- The following features were implemented :
- Communication can happen between any host (not just localhost)
- The server can handle multiple clients.
- We have used fork() to spawn a new child process to take care of the clients' needs instead of creating new threads for each new client.
- Connection is opened using TCP stream socket
- All 9 required functionalities along with possible error handling capabilities have been implemented. Additional 'help' has also been provided.
- A command other than these 9 would result in an error.
- Two different sockets have been implemented, one for control flow and another for data flow. The data port would be provided by the client to the server. Both the sockets are handled simultaneously by both the client and the server.
- All possible errors with the above 9 commands have been taken care of. In case of an error at the server, it would be sent to the client through the control socket and the client will in turn display it on the screen (stdout).
- Every kind of transfer other than data happens through the control socket. Data flow is through the data socket.
- End of file transfer has been indicated as follows. We consider the situation of 'get'.
- After every read from the file, the server sends the read data through the data socket along with some control information through the control socket.
- If end of file has not been reached, the server sends "FSR" which stands for 'File Still Remaining' to the client through the control socket.
- The client receives the data and the control information simultaneously. It reads from the data socket, writes to the file and reads from the control socket and checks if the file is still remaining or not. If it reads 'FSR', it knows that file is still yet to come.
- When end of file is reached, the server sends "EOF" through the control socket along with some final piece of data (through data socket).
- When the client received 'EOF', it writes the last piece of data received from the data stream and closes the file.
- Trimming of commands has been done (removing the whitespaces etc.) both internally and externally.
II. Limitations :
- We have not followed the RFC 959 documentation by J. Postel & J. Reynolds for reply codes etc. As a result, our code may not be work with a general ftp server.
III. How to Run :
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In the compressed file being submitted, these are the file lists :
tcpSocket.h Declaration of functions & constants related to tcpSocket class tcpSocket.cpp Implementation of functions of tcpSocket class ftpClient.h Declaration of functions & constants related to ftpClient class ftpClient.cpp Implementation of functions of ftpClient & contains main function ftpServer.h Declaration of functions & constants related to ftpServer class ftpServer.cpp Implementation of functions of ftpServer & contains main function
The header files (.h) are inside the 'include' folder.
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Building and Running :
Simply run "make"(without quotes) ~ $ make
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Typing "make" will compile the codes and create two executables named 'ftpClient' and 'ftpServer'. If you want to remove the exexutables, type "make clean".
~ $ ./ftpServer
Server Program for FTP
Amit Mittal & Rahul Radhakrishnan, IIT Guwahati
Successfully started on PORT: 8182
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Now, the server is up and running and listening for a connection.
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For running the client program, for eg,
~ $ ./ftpClient
Client Program for FTP
Amit Mittal & Rahul Radhakrishnan, IIT Guwahati
Usage : ./ftpClient Hostname Port
-- Hostname refers to the hostname/IP address of the server -- Port refers to the server's control port (8182 in our case)
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To connect the client to the running and listening FTP server, type (for eg.)
~$ ./ftpClient 10.4.32.17 8182 -
This will connect the client to the server and various operations like cd, !cd, get, put, pwd, ls etc. can be performed.
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Run FTP Server ~ $ ./ftpServer
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Run FTP Client ~ $ ./ftpClient server_address server_port
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IV. Changing parameters of the code :
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There will not be much need to change the parameters of the programs. But if needed, several values are defined using the "#define" macro, in the various header files, which can be changed. They are listed as follows :
- #define CLIENT_PORT 20000 : The client's port
- #define INITPORT 23456 : Initial port of server
- #define MAX_CMD_LEN 1024 : Max. length of a command (get, put, cd etc.)
- #define DEBUG 0 : Can be set to 1 to see additional statements which are otherwise not printed.
- #define BACKLOG 10 : This is used in the listen function (max. length of queue).
- #define CONTROL_PORT 8182 : This is the value of the control port for exchanging control information between client and server.
- #define MAXBUFFSIZE 1024 : This is the maximum length of the buffer
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Other than these parameters listed, nothing else needs to be changed.
V. Details of Code :
The general implementation details have been given in the beginning.
This code has been implemented in file tcpSocket.cpp and the configuration of the socket is in file tcpSocket.h
This code has been implemented in file ftpServer.cpp and the configuration of the ftp server is in file tcpSocket.h
This code has been implemented in file ftpClient.cpp and the configuration of the ftp client is in file tcpSocket.h
VI. Sample Input/Output :
server_address = 10.4.21.9 server_port = 8182
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Build the 2 files INPUT: $make
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Run the ftp server INPUT: $./ftpServer OUTPUT(on server side): Successfully started on PORT: 8182
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Now, run the ftp client INPUT: $./ftpClient 10.4.21.9 8182 OUTPUT(on client side): Successfully connected to server (control socket): 10.4.21.9 Successfully started on PORT: 20000 Successfully connected to server(data port) Type 'help' for more info
INPUT: ftp> help OUTPUT(on client side): Options available: 1. !ls 2. !cd 3. !pwd 4. ls 5. cd 6. pwd 7. get 8. put 9. quit
INPUT: ftp> !pwd OUTPUT(on client side): /home/pirate/Dropbox/PROJECTS/network_lab/assignment3/assignment3 - modified
INPUT: ftp> !cd include OUTPUT(on client side): Changing directory to: include Directory successfully changed.
INPUT: ftp> !cd OUTPUT(on client side): Changing directory to: /home/pirate Directory successfully changed.
INPUT: ftp> !ls -l OUTPUT(on client side): Result is total 72 -rwxr-xr-x 1 pirate pirate 24190 Mar 11 13:40 ftpClient -rw-r--r-- 1 pirate pirate 2978 Mar 11 13:52 ftpClient.cpp -rwxr-xr-x 1 pirate pirate 24383 Mar 11 13:40 ftpServer -rw-r--r-- 1 pirate pirate 2919 Mar 11 13:52 ftpServer.cpp drwxr-xr-x 2 pirate pirate 4096 Mar 9 22:02 include -rw-r--r-- 1 pirate pirate 158 Mar 8 11:22 makefile -rw-r--r-- 1 pirate pirate 86 Mar 8 09:35 README.md -rw-r--r-- 1 pirate pirate 3379 Mar 11 10:21 tcpSocket.cpp
INPUT: ftp> ls OUTPUT(on client side): ftpClient ftpClient.cpp ftpServer ftpServer.cpp include makefile README README~ tcpSocket.cpp ls successfully executed in server
INPUT:
ftp> pwd
OUTPUT(on client side):
/home/pirate/Dropbox/PROJECTS/network_lab/assignment3/assignment3 - modified
pwd successfully executed in server
INPUT:
ftp> put Assignment_3.pdf
OUTPUT(on client side):
Size of file transferred : 128.33691 KiB
File transfer to server successful
File successfully received in server
INPUT:
ftp> get sample.jpeg
OUTPUT(on client side):
Size of file received : 39.71777 KiB
File successfully received from server
File successfully sent from server