sockets's Introduction

code for creating sockets

for teaching/learning about sockets the underlying TCP transport layer comms channel for all internet protocols

echo

see server.py the process logs to socket.log (appends, you may have to delete old)

server side

run in background ./server.py &
- binds to 127.0.0.1:8111
- check it with netstat -lan |less note the state LISTEN
- if it crashes or has just ended the ip&port may still be bound, in a TIME_WAIT status instead of LISTEN, you can see this through netstat, you will have to wait for it to end

client side, talk to server

fake out client comms with netcat nc -v -n 127.0.0.1 8111
- will echo the data you type in back at you
- quit will end the connection
- check the socket source & dest while you are talking to the server `netstat -lan|les

Questons:

To answer these you may need to have a couple of terminal sessions open, it's easier.

Running the server as is

Can you talk to it from another user on the same box? Why or why not?
Can you talk to it from another box? Why or why not?
Can you run the server code many times in the background? Why or why not?

Copy the code to server2.py, change the port, choose a port in the range 8000-8999 that you are not using. 2. run both ./server.py & and ./server2.py & at the same time, in the background 3. does it work? Why or why not? 4. can you talk to each of them, using nc what do you need to change to talk to the 2nd server

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