+@item
+This header file does not define the type @code{socklen_t} on some platforms:
+HP-UX 10.20, IRIX 6.5, OSF/1 4.0, Interix 3.5, BeOS.
+@item
+This header file does not define the type @code{struct iovec} on some platforms:
+OpenBSD 4.4.
+@item
+This header file is lacking the @code{SHUT_RD}, @code{SHUT_WR},
+@code{SHUT_RDWR} macros on some platforms, despite having the @code{shutdown}
+functions:
+emx+gcc.
+@item
+The @code{struct sockaddr_storage} type does not have a member @code{ss_family}
+on some platforms:
+AIX 7.1.