server: split away networking code.

1 files changed, 149 insertions, 0 deletions

diff --git a/src/server/net.c b/src/server/net.c
new file mode 100644
index 0000000..cecf10c
--- /dev/null
+++ b/src/server/net.c
@@ -0,0 +1,149 @@
+/*
+ * Hot Beverage Companion – desktop app network module
+ *
+ * Copyright (C) 2017 Gediminas Jakutis
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; version 2.1
+ * of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <netinet/udp.h>
+#include <poll.h>
+#include <unistd.h>
+#include <string.h>
+#include <time.h>
+#include <stdlib.h>
+#include "net.h"
+
+struct netstate_internal {
+	int (*getlastdata)(char * const data, struct netstate * const state);
+	unsigned int handle;
+	struct timespec lastreply;
+	int sock;
+};
+
+static int dolisten(char * const data, struct netstate_internal * const state);
+static int getpacket(char *data, size_t buffsize, int sock, struct sockaddr_in *sender);
+static int getlastdata_internal(char * const data, struct netstate * const state);
+
+struct netstate *net_init(const unsigned int port)
+{
+	struct netstate_internal *ret;
+	struct sockaddr_in bindaddress = {0};
+
+	ret = malloc(sizeof(struct netstate_internal));
+	bindaddress.sin_family = AF_INET;
+	bindaddress.sin_port = htons(port);
+	ret->sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	if (bind(ret->sock, (struct sockaddr*) &bindaddress, sizeof(bindaddress))) {
+		free(ret);
+		return NULL;
+	}
+
+	clock_gettime(CLOCK_MONOTONIC_RAW, &ret->lastreply);
+	ret->lastreply.tv_sec -= 5;
+	ret->handle = 0; /* currently unused */
+	ret->getlastdata = &getlastdata_internal;
+
+	return (struct netstate *) ret;
+}
+
+int net_close(struct netstate **state) {
+	close((*(struct netstate_internal **)state)->sock);
+	free(*state);
+	*state = NULL;
+	return 0;
+}
+
+static int dolisten(char * const data, struct netstate_internal * const state)
+{
+	char buff[9001] = {0};
+	static const char servermagic[] = "I love coffee!";
+	static const char clientmagic[] = "I love tea!";
+	struct timespec now;
+	struct timespec wait = {0, 25 * 1000 * 1000};
+	struct sockaddr_in clientaddr;
+	size_t i = 10;
+	int ret;
+
+	do {
+		clock_gettime(CLOCK_MONOTONIC_RAW, &now);
+		ret = getpacket(buff, sizeof(buff), state->sock, &clientaddr);
+
+		switch (ret) {
+		case NET_OK:
+			state->lastreply = now;
+			if (buff[0] == 'I') {
+				if (!(strcmp(buff, servermagic))) {
+					sendto(state->sock, clientmagic, sizeof(clientmagic),
+							MSG_DONTWAIT, (struct sockaddr *) &clientaddr, sizeof(clientaddr));
+				}
+				ret = NET_NONEWDATA; /* consume packet and lie about it */
+				continue;
+			} else {
+				memcpy(data, buff, 8ul);
+			}
+			break;
+		default:
+			; /* noop */
+		}
+
+		if (!ret) {
+			nanosleep(&wait, NULL);
+		}
+	} while (--i && ret != 0);
+
+	/* no packets in five seconds */
+	if ((now.tv_sec - state->lastreply.tv_sec) >= 5) {
+		ret = NET_DEAD;
+	}
+
+	return ret;
+}
+
+static int getpacket(char *data, size_t buffsize, int sock, struct sockaddr_in *sender)
+{
+	static struct pollfd pfd = {0};
+	int ret;
+	socklen_t sender_len = sizeof(*sender);
+
+	if (!pfd.fd) {
+		pfd.fd = sock;
+		pfd.events = POLLIN;
+		pfd.revents = 0;
+	}
+
+	ret = poll(&pfd, 1, 0);
+	if (ret < 0) {
+		/* NOOP */
+	} else if (!ret) {
+		ret = NET_NONEWDATA;
+	} else if (pfd.revents & POLLIN) {
+		recvfrom(sock, data, buffsize, MSG_DONTWAIT, (struct sockaddr *) sender, &sender_len);
+		ret = NET_OK;
+	} else {
+		ret = NET_NONEWDATA;
+	}
+
+	return ret;
+}
+
+
+static int getlastdata_internal(char * const data, struct netstate * const state)
+{
+	return dolisten(data, (struct netstate_internal *) state);
+}