python 循环套接字连接

Question

Question regarding the python socket package

My goal is to create a simple.network port scanner. This is the basic idea:

#List of ports to scan
ports = [20,21,22,23,25,80]

#dictionary of port statuses
port_status = {}

#Create socket:
MY_SOCK = s.socket(s.AF_INET, s.SOCK_STREAM)

#For loop to scan each port
for port in ports:
    TARGET = ("192.168.12.123", port)
    
    #If connection is successful, result should be int 0
    result = MY_SOCK.connect_ex(TARGET)

    #save port and status as key/pair value
    port_status[port] = result

    #Terminate socket
    MY_SOCK.shutdown(s.SHUT_RDWR)
    MY_SOCK.close()

I am having an issue that after the first successful socket connection, it doesn't restart properly for the following sockets.

With the syntax shown above, I get thrown an OSerror

if I don't do a shutdown, it makes one successful connection then doesn't connect to the following ports.

There must be something wrong with my closing of the socket.

Any advice? Many thanks

Answer 1

By running it line by line outside the loop, I managed to pinpoint the problem.

The issue is that if a connection fails, it throws an error because it could not terminate a failed connection

I solved it (incorporating h4z3's advice to move the socket creation into the for loop) in the following way:

for port in ports:
    MY_SOCK = s.socket(s.AF_INET, s.SOCK_STREAM)
    TARGET = ("192.168.12.123", port)
    result = MY_SOCK.connect_ex(TARGET)
    port_status[port] = result

    #Only attempt to close connection if connection was successful (== 0)
    if result == 0:
        MY_SOCK.shutdown(s.SHUT_RDWR)
        MY_SOCK.close()

Thanks for the assistance