Sockets - How to find out what port and address I m assigned

Question

I m having trouble figuring this out - I m working with sockets in C using this guide - http   binarii com files papers c sockets txt  I m trying to automatically get my ip and port using   server sin port   0                  bind   will choose a random port   server sin addr s addr   INADDR ANY      puts server s IP automatically            bind int fd  struct sockaddr  my addr int addrlen      Bind function   After a successful bind  how do I find out what IP and Port I m actually assigned

User · Answer

The comment in your code is wrong  INADDR ANY doesn t put server s IP automatically   It essentially puts 0 0 0 0  for the reasons explained in mark4o s answer

User · Answer

If it s a server socket  you should call listen   on your socket  and then getsockname   to find the port number on which it is listening   struct sockaddr in sin  socklen t len   sizeof sin   if  getsockname sock   struct sockaddr    amp sin   amp len     -1      perror  getsockname    else     printf  port number  d n   ntohs sin sin port      As for the IP address  if you use INADDR ANY then the server socket can accept connections to any of the machine s IP addresses and the server socket itself does not have a specific IP address   For example if your machine has two IP addresses then you might get two incoming connections on this server socket  each with a different local IP address   You can use getsockname   on the socket for a specific connection  which you get from accept    in order to find out which local IP address is being used on that connection

[c] Sockets - How to find out what port and address I'm assigned

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