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code/demand-accept.c

+/* demand-accept.c
+ *
+ * Copyright (c) 2000 Sean Walton and Macmillan Publishers.  Use may be in
+ * whole or in part in accordance to the General Public License (GPL).
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+*/
+
+/*****************************************************************************/
+/*** demand-accept.c                                                       ***/
+/***                                                                       ***/
+/*** Accept connections based on signal demand.  When a connection is made,***/
+/*** a SIGIO  is raised and the process stops to handle it.  The handler   ***/
+/*** connects to the client.  The main program could be processing other   ***/
+/*** tasks when these connections arrive.                                  ***/
+/*****************************************************************************/
+
+#include <stdio.h>
+#include <sys/socket.h>
+#include <resolv.h>
+#include <signal.h>
+#include <fcntl.h>
+
+void PANIC(char* msg);
+#define PANIC(msg) { perror(msg); abort(); }
+
+int sd;
+
+/*--------------------------------------------------------------------*/
+/*--- Signal capture: SIGIO - connect to client.                   ---*/
+/*--------------------------------------------------------------------*/
+void sig_io(int sig)
+{	int client;
+
+	client = accept(sd, 0, 0);
+	send(client, "hello\ngoodbye!\n\n", 16, 0);
+	close(client);
+}
+
+/*--------------------------------------------------------------------*/
+/*--- main - set up asynchronous connections and wait              ---*/
+/*--------------------------------------------------------------------*/
+int main()
+{	int flag=64;
+	struct sockaddr_in addr;
+	struct sigaction act;
+
+	bzero(&act, sizeof(act));
+	act.sa_handler = sig_io;
+	if ( sigaction(SIGIO, &act, 0) < 0 )
+		PANIC("SigAction");
+	sd = socket(PF_INET, SOCK_STREAM, 0);
+	bzero(&addr, sizeof(addr));
+	addr.sin_family = AF_INET;
+	addr.sin_port = htons(9999);
+	addr.sin_addr.s_addr = INADDR_ANY;
+	if ( bind(sd, (struct sockaddr*)&addr, sizeof(addr)) != 0 )
+		PANIC("bind");
+	if ( listen(sd, 20) != 0 )
+		PANIC("listen");
+	if ( fcntl(sd, F_SETFL, O_ASYNC | O_NONBLOCK) < 0 )
+		PANIC("async & nonblocking");
+	if ( fcntl(sd, F_SETOWN, getpid()) < 0 )
+		PANIC("setown");
+	while (1)
+		sleep(5);
+	return 0;
+}