socket error errno 99 cannot assign requested address and namespace in python

Question

My server software says errno99  cannot assign requested address while using an ip address other than 127 0 0 1 for binding   But if the IP address is 127 0 0 1 it works  Is it related to namespaces   I am executing my server and client codes in another python program by calling execfile    I am actually editing the mininet source code I edited net py and inside that I used execfile  server py   execfile  client1 py   and execfile  client2 py   So as soon as  sudo mn --topo single 3  is called along with the creation of 3 hosts my server and client codes will get executed I have given my server and client codes below    server code import select  import socket  import sys  backlog   5  size   1024  server   socket socket socket AF INET  socket SOCK STREAM   server bind   10 0 0 1  9999    server listen backlog   input    server   running   1  while running       inputready outputready exceptready   select select input             for s in inputready           if s    server               client  address   server accept                input append client          else               l   s recv 1024              sys stdout write l  server close        client code import socket import select import sys import time while 1        s addr server1 accept           data int s recv 4       s   socket socket       s connect   10 0 0 1  9999       while  1           f open   hello1 txt    rb           l   f read 1024          s send l          l   f read 1024          time sleep 5  s close

User · Answer

when you bind localhost or 127 0 0 1  it means you can only connect to your service from local   you cannot bind 10 0 0 1 because it not belong to you  you can only bind ip owned by your computer  you can bind 0 0 0 0 because it means all ip on your computer  so any ip can connect to your service if they can connect to any of your ip

User · Answer

This error will also appear if you try to connect to an exposed port from within a Docker container  when nothing is actively serving the port  On a host where nothing is listening bound to that port you d get a No connection could be made because the target machine actively refused it error instead when making a request to a local URL that is not served  eg  localhost 5000  However  if you start a container that binds to the port  but there is no server running inside of it actually serving the port  any requests to that port on localhost will result in    Errno 99  Cannot assign requested address  if called from within the container   or  Errno 0  Error  if called from outside of the container     You can reproduce this error and the behaviour described above as follows  Start a dummy container  note  this will pull the python image if not found locally   docker run --name serv1 -p 5000 5000 -dit python  Then for  Errno 0  Error enter a Python console on host  while for  Errno 99  Cannot assign requested address access a Python console on the container by calling  docker exec -it -u 0 serv1 python  And then in either case call  import urllib request urllib request urlopen  https   localhost 5000    I concluded with treating either of these errors as equivalent to No connection could be made because the target machine actively refused it rather than trying to fix their cause - although please advise if that s a bad idea   I ve spent over a day figuring this one out  given that all resources and answers I could find on the  Errno 99  Cannot assign requested address point in the direction of binding to an occupied port  connecting to an invalid IP  sysctl conflicts  docker network issues  TIME WAIT being incorrect  and many more things  Therefore I wanted to leave this answer here  despite not being a direct answer to the question at hand  given that it can be a common cause for the error described in this question

User · Answer

Try like this     server bind   0 0 0 0   6677

User · Answer

Stripping things down to basics this is what you would want to test with   import socket server   socket socket    server bind   10 0 0 1   6677    server listen 4   client socket  client address   server accept   print client address   has connected   while 1  1      recvieved data   client socket recv 1024      print recvieved data    This works assuming a few things    Your local IP address  on the server  is 10 0 0 1  This video shows you how  No other software is listening on port 6677   Also note the basic concept of IP addresses   Try the following  open the start menu  in the  search  field type cmd and press enter  Once the black console opens up type ping www google com and this should give you and IP address for google  This address is googles local IP and they bind to that and obviously you can not bind to an IP address owned by google   With that in mind  you own your own set of IP addresses  First you have the local IP of the server  but then you have the local IP of your house  In the below picture 192 168 1 50 is the local IP of the server which you can bind to  You still own 83 55 102 40 but the problem is that it s owned by the Router and not your server  So even if you visit http   whatsmyip com and that tells you that your IP is 83 55 102 40 that is not the case because it can only see where you re coming from   and you re accessing your internet from a router     In order for your friends to access your server  which is bound to 192 168 1 50  you need to forward port 6677 to 192 168 1 50 and this is done in your router  Assuming you are behind one   If you re in school there s other dilemmas and routers in the way most likely

[python] socket.error:[errno 99] cannot assign requested address and namespace in python

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