I do recommend:
- libboost: http://www.boost.org/doc/libs/1_35_0/doc/html/boost_asio/reference/ip__tcp/socket.html
- Qt: http://qt-project.org/doc/qt-5.0/qtnetwork/examples-network.html
Both are multiplatform and very good libraries, but Qt is for GUIs more than a simple library, so think about using libboost for this single purpose.