The ultimate socket library for C and C++, supporting TCP, UDP and Unix sockets (DGRAM and STREAM) on Linux, FreeBSD, Solaris. Only ZMQ is better. Developer's documentation:
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Release allocated memory by getaddrinfo - memory leak fix

README for libsocket

Travis Build Status

(Pre-built documentation for libsocket developers can be found on my server)

BUILDING libsocket

If you want to install both libsocket and libsocket++, simply use this command:

$ cmake CMakeLists.txt
$ make
# make install

This installs the SOs and to /usr/lib/ and the header files to /usr/include/libsocket. You may change these paths in the CMakeLists.txt file in the project root.

Note the changed library name on SunOS.

CMake is required to support object libraries, which is the case in versions higher than or equal to 2.8.


libsocket is a library with a C part and a C++ part making sockets usage easy and clean.

Using the C part:

  • Link against
  • Functions combining more than one operation on sockets (e.g. create and connect TCP socket)
  • Main principle: "One function to connect a socket, one to close it."

Using the C++ part:

  • Link against
  • Classes representing the different socket types, e.g. TCP client sockets, UNIX DGRAM "server" sockets
  • Complex (almost complicated...) class hierarchy (doc/libsocket++/classes.svg) providing the possibility of extensive and intensive code sharing.
  • C++ish implementation (features include overloaded stream (<<, >>) operators, functions accepting std::string objects and more-or-less STL use), so -> good integration in other applications or libraries.
  • Using C++11 features: The copy constructor of the socket base class is deleted; this enables the destructor to safely close the socket when it leaves the visible scope. Some functions are internally using unique_ptrs to enable safe deallocation.


The libsocket library supports following things and protocols:

  • IPv4 (client, server)
  • IPv6 (client, server; if your machine supports it)
  • TCP (client, server)
  • UDP (client, server -- the difference is that client sockets may be connected to an endpoint)
  • UNIX Domain Sockets (DGRAM/STREAM server/client)
  • IPv4/IPv6 multicast (only in C)
  • Abstraction classes for select(2) and epoll(7) (C++)
  • Easy use (one function call to get a socket up and running, another one to close it)
  • RAII, no-copy classes -- resource leaks are hard to do.
  • Proper error processing (using errno, gai_strerror() etc.) and C++ exceptions.

One of the main advantages of libsocket is that you don't have to write the complex and error-prone procedures for connecting a socket, checking it for errors etc. yourself. Your networking programs become shorter and better readable.

libsocket supports the important socket types: INET/INET6 with TCP and UDP; and UNIX DGRAM/STREAM.

Almost every function working with sockets is wrapped by libsocket, e.g.:

  • sendto
  • recvfrom
  • accept
  • socket/connect - one function
  • socket/bind - one function

libsocket is designed to not use a "proprietary" socket format (as libc does with its FILE type) giving you the possibility to operate on the raw file descriptor with functions other than those provided by libsocket.



Libsocket works best on modern linux systems. It needs a C++11 compiler like g++ or clang++. Override the default compiler using the flag -DCMAKE_CXX_COMPILER=<compiler> or -DCMAKE_C_COMPILER=<compiler>.


Other than on Linux systems libsocket is known to work as well (although not really thoroughly tested) on FreeBSD systems with working C++11 stack. The library has been tested on a FreeBSD 10.0-RC4 amd64 system using the shipped compilers (which is clang 3.3).

SunOS: OpenIndiana, (Solaris?)

The library part written in C works (partly) also on OpenIndiana; this has been verified using SunOS openindiana 5.11 oi_151a8.

Because a modern C++ compiler was not available at the time of testing, the C++ library part is not built on SunOS systems.

Another difficulty is the existence of the system library libsocket; therefore the C library is renamed to libsocket_hl on SunOS. You have to link your programs using the flag -lsocket_hl, not -lsocket.

SunOS limitations

  • The UDP server example (examples/echo_dgram_server.c) refuses to create a socket. The error is "Operation not supported on transport endpoint".
  • The TCP server example (examples/transmission_server.c) also fails when trying to create the socket. Here, the error displayed is "Invalid argument". I'm quite sure that these issues can be fixed with a little investigation and knowledge of SunOS.


libsocket does not work on OpenBSD yet because there are some more fundamental source level incompatibilities than those between Linux and FreeBSD/OpenIndiana-SunOS.

Other OSs

If you're using libsocket successfully on other platforms (or even ported it), please let me know.

How to use the libsocket: static vs. dynamic

Static Linkage

It's possible to link libsocket statically into your program (by placing the .c[pp] and .h[pp] files in your source tree or linking against a .a file). You don't have to mind legal issues because libsocket is licensed by a slightly modified 2-clause BSD license which permits any use, as long as you include the license text in your product (so it's clear that libsocket is licensed by this License) and the notice that we wrote libsocket (as described in the license). It's ok to mention libsocket in your product's Readme or advertisements anyway.

Dynamic Linkage

The recommended method to use libsocket is to link your program against the libsocket SO (DLL). Using this method is quite easy; you have to compile the dynamic libraries (libsocket and libsocket++) using the Makefile (see section "BUILDING")

Linking your programs against the library is also simple: if $OBJECTS are your object files, then link them together using one of these commands:

    $ gcc -o yourprog -lsocket $OBJECTS
    # or
    $ g++ -o yourprog -lsocket++ $OBJECTS

You only need to link against one library, even when using C++, because libsocket++ contains all necessary functions.

If you distribute your program in binary form, it's possible to distribute the library binaries along with your program and install them along your program.


You may test libsocket and make some experiences by playing with the examples provided in the standard libsocket distribution in examples/ and examples++. More detailed descriptions can be found in the source files. The collection of examples contain (among others):


  • http.c: A simple http client
  • echo_dgram_server.c, echo_dgram_client.c, echo_dgram_connect_client.c: Shows how to use UDP sockets, both in connected and unconnected mode.
  • unix_stream_client.c, unix_stream_server.c: Demonstrating UNIX STREAM sockets as echo server/client
  • unix_dgram_client.c, unix_dgram_server.c: Demonstrating UNIX DGRAM sockets as simple server/client transmitting text.
  • multicast-listen.c: Demonstrating how to use libinetsocket for multicast networking.

Build these with gcc -o <outfile> -lsocket <example-name>.


  • http.cpp, http_2.cpp: Two simple HTTP clients using slightly different approaches
  • server.cpp, client.cpp: TCP client and server
  • unix_client_dgram.cpp: Writes a message to the syslog using UNIX DGRAM sockets
  • echo_server.cpp, echo_client_conn.cpp, echo_client_sndto.cpp: UDP client/server (two clients: One using sendto(), another using connected datagram sockets)
  • unix_client_stream.cpp, unix_server_stream.cpp: Client/Server using UNIX STREAM sockets.

Build these with [clan]g++ -std=c++11 -lsocket++ -o <outfile> <example-name>.

You should have a look at the length of the code; while http.c is complete with 24 sloc (source lines of code) - the quite similar client simple-http ( uses almost 70 lines of code.