netcat implementation

in this project we will implement basic implementation of netcat.

we will support the following features:

1. -e flag: execute a shell command
2. -i flag: get input from a socket
3. -o flag: write output to a socket
4. -b flag: input and output go to the same socket
5. -t flag: set timeout for the execution of the program

if we don't send the -e flag, the program will act as a chat between two terminals. (if we send -i or -o flags, the chat will be one-way channel)

we will support the following socket types:

1. TCP - as client & server. can get input, output or both from a socket.
2. UDP - as client & server. can get input, output or both from a socket.
3. UNIX Domain Socket Stream - as client & server. can get input, output or both from a socket.
4. UNIX Domain Socket Datagram - as client & server. server can get input, client will send output.

to use the socket we will send them after the flag, in this format:

1. TCP server: TCPS<PORT>
2. TCP client: TCPC<HOST>,<PORT>
3. UDP server: UDPS<PORT>
4. UDP client: UDPC<HOST>,<PORT>
5. UDS stream server: UDSSS<PATH>
6. UDS stream client: UDSCS<PATH>
7. UDS datagram server: UDSSD<PATH> (go only with -i flag)
8. UDS datagram client: UDSCD<PATH> (go only with -o flag)

NOTE: all datagram sockets (UDP and UDS datagram) will be wait for a dummy input from the client for accepting the connection, and then start the execution of the program.

example usage:

in all of the examples below, when we use the -e flag, we will execute the command a tik tak toe game, that we implemented in the here

we simulate a server & client with nc command,and for the unix domain socket datagram we use socat command.

all of the commands that you can use are in the run_commands file.

1. open a TCP server and wait for a input from a client. output go to stdout

# server
./mync -e "./ttt 123456789" -i TCPS4269
# client
nc localhost 4269

2. open a TCP server and wait for a input from a client. output go to client

# server
./mync -e "./ttt 123456789" -b TCPS4269
# client
nc localhost 4269

3. open a UDP server and wait for a input from a client, the output go to TCP server that listen on port 6699

# TCP server
nc -l -p 6699
# UDP server & TCP client
./mync -e "./ttt 123456789" -i UDPS4269 -o TCPClocalhost,6699
# UDP client
nc -u localhost 4269

4. open a UDS stream server and wait for a input from a client, the output go to TCP server that listen on port 6699

# TCP server
nc -l -p 6699
# UDS stream server & TCP client
./mync -e "./ttt 123456789" -i UDSSShoi.socket -o TCPClocalhost,6699
# UDS stream client
nc -U hoi.socket

5. open a UDS datagram server & UDP server, the input is from the UDS client and the output go to the UDP client

# servers
./mync -e "./ttt 123456789" -i UDSSDhoi.socket -o UDPS4269
# UDS client
socat - UNIX-SENDTO:hoi.socket
# UDP client
nc -u localhost 4269

6. chat between two terminals

# terminal 1
./mync -b TCPS4269
# terminal 2
./mync -b TCPClocalhost,4269

7. input from UDS server and output to UDS client (datagram)

#open the UDS server (the output will go here)
socat UNIX-RECVFROM:hoi1.socket,fork -
# open the UDS client for sending the output, and the UDS server for input
./mync -e "./ttt 123456789" -o UDSCDhoi1.socket -i UDSSDhoi2.socket
# open the UDS client for sending the input
socat - UNIX-SENDTO:hoi2.socket

8. Unix domain socket stream server and client

# example 1
    #open the UDS stream server
    nc -lU hoi.socket
    # open the UDS stream client
    ./mync -e "./ttt 123456789" -b UDSCShoi.socket
# example 2
    ./mync -e "./ttt 123456789" -b UDSSShoi.socket
    nc -U hoi.socket

code coverage

we checked the code coverage of the code using gcov. most of the code is covered, except errors that are related to the socket library.

link to the code coverage report