Client & Server Sockets & Exceptions

Question 1

This demonstrates that, from an OS perspective, different either a client or a server.

Answer 1

NOPE once a socket is created it is neutral, can be used for both

Question 2

The host part of the server address can be either

Answer 2

hostname, ip or empty string

‘127.0.0.1’ or ‘localhost’ loopback address

if hostname it used DNS but non-deterministic and may return IPv4 or IPv6

empty string a server can accept IPv4 connections on all available interfaces

Question 3

Port numbers range

Answer 3

0 - 65535

0-1023 well-known
1024 - 49151 registered
49152 - 65535 dynamic, private and ephemeral

when socket bound to address, cannot be changed (cannot bind twice)

when closed the binding is released but not immediately (TCP WAIT_TIME)

Question 4

s = socket(AF_INET,SOCK_STREAM)
print(s)
s.bind((SERVER_HOST,SERVER_PORT))
print(s)

Answer 4

after binding we get the laddr

Question 5

What about binding on the client side?

Answer 5

happens implicitly (to local address with ephemeral port)

Question 6

how to know client port on client side vs. server port?

Answer 6

cs.getsockname()
cs.getpeername()

Question 7

If you try to call the listen
method without binding

Answer 7

it will raise an OSError Exception.

Question 8

regular sockets vs. listening sockets

Answer 8

server client
vs
server

Question 9

which function accepts the optional backlog parameter

what does it do

Answer 9

listen()

determines the how many connections can be pending before refusing other connections
1 - socket.SOMAXCONN

128 linus
5-200 windows

Question 10

On Windows, to verify that a socket is listening on a specific port, use the following
command on cmd:

Answer 10

netstat -aon

Question 11

What method puts the program into blocking mode?

Answer 11

accept()

returns connection (regular socket for send\recv) and address

Question 12

examples of gaierror exceptions

Answer 12

getaddrinfo(“ “, 80)
gethostbyname(‘gooogggle.com’)
gethostbyaddr(‘127.412.14.10’)
or anything with a weird ip

connect((‘hello’, 70000))
bind((‘hellobitch’, 80000))

Question 13

what functions could cause timeoutError

Answer 13

at client
connect()
create_connection ()
recv()

at server
accept()
recv()

Question 14

s = socket()
s.bind((‘localhost’,800000))

Answer 14

overflowError

Question 15

s.send(‘hello’)

Answer 15

TypeError

Question 16

in_msg = s.recv(-5)

Answer 16

valueError

Question 17

print(s.getsockname()[3])

Answer 17

index error

Question 18

s.receivall(1024)

Answer 18

attributeError