static struct linger  linger = {0, 0};
 int lsize  = sizeof(struct linger);
 setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, lsize);

 

 ---------------------

  SO_LINGER (see following NOTE) controls the action taken when unsent
  messages are queued on socket and a close(S) is performed. If the socket
  promises reliable delivery of data and SO_LINGER is set, the system will
  block the process on the close attempt until it is able to transmit the
  data or until it decides it is unable to deliver the information. A timeout
:
  period, termed the linger interval, is specified in the setsockopt call
  when SO_LINGER is requested. If SO_LINGER is disabled and a close is
  issued, the system will process the close in a manner that allows the
  process to continue as quickly as possible.

  NOTE: Due to artifacts of the current implementation, the linger option no
  longer has an effect. It is still recognized by the system for backward
  compatibility. Currently, close operations complete as expeditiously as
  possible. If unsent data remains, the protocols will ensure its delivery.