socketpair - create a pair of connected sockets


   #include <sys/types.h>          /* See NOTES */
   #include <sys/socket.h>

   int socketpair(int domain, int type, int protocol, int sv[2]);


   The  socketpair()  call creates an unnamed pair of connected sockets in
   the specified domain, of the specified type, and using  the  optionally
   specified  protocol.   For  further  details  of  these  arguments, see

   The file descriptors used in referencing the new sockets  are  returned
   in sv[0] and sv[1].  The two sockets are indistinguishable.


   On  success,  zero is returned.  On error, -1 is returned, and errno is
   set appropriately.

   On Linux (and other  systems),  socketpair()  does  not  modify  sv  on
   failure.   A  requirement  standardizing  this  behavior  was  added in


          The specified address family is not supported on this machine.

   EFAULT The address sv does not specify a  valid  part  of  the  process
          address space.

   EMFILE The per-process limit on the number of open file descriptors has
          been reached.

   ENFILE The system-wide limit on the total number of open files has been

          The  specified  protocol  does  not  support  creation of socket

          The specified protocol is not supported on this machine.


   POSIX.1-2001, POSIX.1-2008, 4.4BSD.   socketpair()  first  appeared  in
   4.2BSD.   It  is  generally portable to/from non-BSD systems supporting
   clones of the BSD socket layer (including System V variants).


   On Linux, the only supported  domain  for  this  call  is  AF_UNIX  (or
   synonymously,   AF_LOCAL).    (Most   implementations   have  the  same

   Since  Linux  2.6.27,  socketpair()  supports  the  SOCK_NONBLOCK   and
   SOCK_CLOEXEC flags in the type argument, as described in socket(2).

   POSIX.1  does  not  require  the  inclusion  of <sys/types.h>, and this
   header file is not required on Linux.  However, some  historical  (BSD)
   implementations  required  this  header file, and portable applications
   are probably wise to include it.


   pipe(2), read(2), socket(2), write(2), socket(7), unix(7)


   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.