Network Programming with C/C++

This software contains a simple client and server program written by using C/C++ socket programming. The aim is to provide a functional demonstartion of the socket API function calls socket(), bind(), connect(), listen(), accept, send() and recv().

Clone the directory to get started. Issuing the command make should produce two binaries: server and client, respectively.

./build/server

run the server and

./build/client

runs the client. Issuing the the commands in this order should give the following output for the server

Server is running
Hello from client

and

Hello message sent
Hello from server

for the client.

You may want to inspect the packet exchange using tcpdump. Example:

$ sudo tcpdump -i lo src port 9001 -n

giving an output like this:

11:03:43.043309 IP 127.0.0.1.9001 > 127.0.0.1.34480: Flags [S.], seq 3587490196, ack 3158623795, win 65483, options [mss 65495,sackOK,TS val 2260310467 ecr 2260310467,nop,wscale 7], length 0
11:03:43.043394 IP 127.0.0.1.9001 > 127.0.0.1.34480: Flags [.], ack 18, win 512, options [nop,nop,TS val 2260310467 ecr 2260310467], length 0
11:03:43.043551 IP 127.0.0.1.9001 > 127.0.0.1.34480: Flags [P.], seq 1:18, ack 18, win 512, options [nop,nop,TS val 2260310467 ecr 2260310467], length 17
11:03:43.043802 IP 127.0.0.1.9001 > 127.0.0.1.34480: Flags [F.], seq 18, ack 19, win 512, options [nop,nop,TS val 2260310467 ecr 2260310467], lenght 0

Tip to use screen for demonstration in a single terminal

For a class room demonstration I use the screen program that allows me to split the terminal windows horizontally (or vertically). I subsequently run the server and the client in different windows. The essential key strokes to control screen are:

• Use CTRL-a S to split the pane horizontally (or CTRL-a | to split vertically)
• Use CTRL-a TAB to toogle between panes
• Use CTRL-a c to create a session with a command prompt in the current pane
• Use CTRL-a d to detach a screen from the TTY and put it in the background
• Use CTRL-a X will close the pane that has focus.

To simplify the prompt I use: PS1='$ '.

See Tom Lee (dot co)'s blog: GNU Screen splitting for additional tips on how to use screen.

Alternativelt, tmux can be used.