TCP_NODELAY undeclared with C++/Linux

[ghost]

Compiling with g++ or clang++ on Ubuntu 18.04 results in the following error:

include/swrap.h: In function ‘int swrapSocket(int, int, char, const char*, const char*)’:
include/swrap.h:171:43: error: ‘TCP_NODELAY’ was not declared in this scope
             setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (void*)&nodelay, sizeof(nodelay));