typedef enum { CTL_TCP_CLOSE_LINGER, CTL_TCP_CLOSE_DONTLINGER } CTL_TCP_SOCKET_CLOSE_TYPE_t;
CTL_TCP_SOCKET_CLOSE_TYPE_t indicates how a socket should be closed.
| linger | timeout | Type of close | Wait for close? |
| CTL_TCP_CLOSE_DONTLINGER | Don't care | Graceful | No |
| CTL_TCP_CLOSE_LINGER | Zero | Hard | No |
| CTL_TCP_CLOSE_LINGER | Nonzero | Graceful | Yes |