Python script returns --> socket.error: [Errno 98] Address already in use

Question

I new to Linux and currently having an issue when running a Python script on my second laptop (strange is that on my other machine the script runs without any issue)

Script that gets executed:

import socket

class DNSQuery:
def __init__(self, data):
self.data=data
self.dominio=''

tipo = (ord(data[2]) >> 3) & 15
if tipo == 0:
ini=12
lon=ord(data[ini])
while lon != 0:
self.dominio+=data[ini+1:ini+lon+1]+'.'
ini+=lon+1
lon=ord(data[ini])

def respuesta(self, ip):
packet=''
if self.dominio:
  packet+=self.data[:2] + "\x81\x80"
  packet+=self.data[4:6] + self.data[4:6] + '\x00\x00\x00\x00'
  packet+=self.data[12:]
  packet+='\xc0\x0c'
  packet+='\x00\x01\x00\x01\x00\x00\x00\x3c\x00\x04'
  packet+=str.join('',map(lambda x: chr(int(x)), ip.split('.')))
  return packet

 if __name__ == '__main__':
 ip='192.168.1.1'
 print 'pyminiDwebconfNS:: dom.query. 60 IN A %s' % ip

 udps = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
 udps.bind(('',53))

try:
while 1:
  data, addr = udps.recvfrom(1024)
  p=DNSQuery(data)
  udps.sendto(p.respuesta(ip), addr)
  print 'Request: %s -> %s' % (p.dominio, ip)
except KeyboardInterrupt:
print 'Finalizando'
udps.close()

Following error occurs:

root@Sn3rpOs /m/r/B4A9-733B# python dns.py 

pyminifakeDwebconfNS:: dom.query. 60 IN A 192.168.1.1
Traceback (most recent call last):
File "dns.py", line 33, in <module>
udps.bind(('',53))
File "/usr/lib/python2.7/socket.py", line 228, in meth
return getattr(self._sock,name)(*args)
socket.error: [Errno 98] Address already in use

I tried already to change the IP adress, but no luck, regardless which IP gets set the error occurs.

Then I checked with "netstat -an" to see if 192.168.1.1 is blocked, but unable to find anything

B4A9-733B# netstat -an

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           
Foreign   Address               State      
tcp        0      0 127.0.0.1:5939          0.0.0.0:*                  
tcp        0      0 127.0.0.1:53            0.0.0.0:*                  
tcp        0      0 127.0.0.2:53            0.0.0.0:*                  
tcp        0      0 127.0.0.1:8118          0.0.0.0:*                   
tcp        0      0 127.0.0.1:9050          0.0.0.0:*                   
tcp        0      0 127.0.0.1:9051          0.0.0.0:*                   
tcp        0      1 192.168.179.135:57008   151.101.193.69:80         
tcp        0   2824 192.168.179.135:57376   151.101.193.69:80       
tcp        0      1 192.168.179.135:34152   151.101.65.69:80        
tcp        0    644 192.168.179.135:50030   151.101.129.69:80       
tcp        0      1 192.168.179.135:34154   151.101.65.69:80        
tcp        0      0 127.0.0.1:9050          127.0.0.1:34242         
tcp        0      0 192.168.179.135:54362   178.62.201.15:9090      
tcp        0      1 192.168.179.135:57014   151.101.193.69:80        
tcp6       0      0 ::1:8118                :::*                        
udp        0      0 127.0.0.1:47649         127.0.0.1:53            
udp        0   2560 0.0.0.0:41994                                    
udp        0      0 127.0.0.1:50619         127.0.0.1:53            
udp        0      0 127.0.0.1:36289         127.0.0.1:53

My problem is that I don fully understand the reported error and what I could check/change to fix this. Hoping you guys can give some additional ideas to get this fixed.

Thanks Chimera

Please indent your code so it will be easy to read and help. — Ofer Arial
– Ofer Arial, Commented Mar 5, 2017 at 14:00

Ofer Arial · Accepted Answer · 2017-03-05 14:08:03Z

1

This line:

udps.bind(('',53))

Is binding the socket so you can listen to INADDR_ANY - any incoming host. It has nothing to do with the ip address "192.168.1.1". The address in use is actually (localhost, 53).

Your error implies that you already have a running program on port 53 (it is occupied) so you can't bind it to the udp port. You can veify that from the netstat, where you see the port is occupied.

Try terminating the process running on port 53 on your machine, and try again.

answered Mar 5, 2017 at 14:08

Ofer Arial

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