Added example to the distribution. Tested on Mac OS

examples/linux/.gitignore

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+mavlink_udp

examples/linux/README

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+A more detailed version of this quickstart is available at:
+
+http://qgroundcontrol.org/dev/mavlink_linux_integration_tutorial
+
+MAVLINK UDP QUICKSTART INSTRUCTIONS
+===================================
+
+MAVLink UDP Example for *nix system (Linux, MacOS, BSD, etc.)
+
+To compile with GCC, just enter:
+
+gcc -I ../../include/common -o mavlink_udp mavlink_udp.c
+
+To run, type:
+
+./mavlink_udp
+
+
+If you run QGroundControl on the same machine, a MAV should pop up.

examples/linux/mavlink_udp.c

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+/*******************************************************************************
+ Copyright (C) 2010  Bryan Godbolt godbolt ( a t ) ualberta.ca
+ 
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+ 
+ 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 General Public License for more details.
+ 
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ 
+ ****************************************************************************/
+/*
+ This program sends some data to qgroundcontrol using the mavlink protocol.  The sent packets
+ cause qgroundcontrol to respond with heartbeats.  Any settings or custom commands sent from
+ qgroundcontrol are printed by this program along with the heartbeats.
+ 
+ 
+ I compiled this program sucessfully on Ubuntu 10.04 with the following command
+ 
+ gcc -I ../../pixhawk/mavlink/include -o udp-server udp-server-test.c
+ 
+ the rt library is needed for the clock_gettime on linux
+ */
+/* These headers are for QNX, but should all be standard on unix/linux */
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <time.h>
+#if (defined __QNX__) | (defined __QNXNTO__)
+/* QNX specific headers */
+#include <unix.h>
+#else
+/* Linux / MacOS POSIX timer headers */
+#include <sys/time.h>
+#include <time.h>
+#include <arpa/inet.h>
+#endif
+
+/* This assumes you have the mavlink headers on your include path
+ or in the same folder as this source file */
+#include <mavlink.h>
+
+
+#define BUFFER_LENGTH 2041 // minimum buffer size that can be used with qnx (I don't know why)
+
+uint64_t microsSinceEpoch();
+
+int main(int argc, char* argv[])
+{
+
+	char help[] = "--help";
+
+
+	char target_ip[100];
+
+	float position[6] = {};
+	int sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	struct sockaddr_in gcAddr; 
+	struct sockaddr_in locAddr;
+	//struct sockaddr_in fromAddr;
+	uint8_t buf[BUFFER_LENGTH];
+	ssize_t recsize;
+	socklen_t fromlen;
+	int bytes_sent;
+	mavlink_message_t msg;
+	uint16_t len;
+	int i = 0;
+	//int success = 0;
+	unsigned int temp = 0;
+
+	// Check if --help flag was used
+	if ((argc == 2) && (strcmp(argv[1], help) == 0))
+    {
+		printf("\n");
+		printf("\tUsage:\n\n");
+		printf("\t");
+		printf("%s", argv[0]);
+		printf(" <ip address of QGroundControl>\n");
+		printf("\tDefault for localhost: udp-server 127.0.0.1\n\n");
+		exit(EXIT_FAILURE);
+    }
+
+
+	// Change the target ip if parameter was given
+	strcpy(target_ip, "127.0.0.1");
+	if (argc == 2)
+    {
+		strcpy(target_ip, argv[1]);
+    }
+
+
+	memset(&locAddr, 0, sizeof(locAddr));
+	locAddr.sin_family = AF_INET;
+	locAddr.sin_addr.s_addr = INADDR_ANY;
+	locAddr.sin_port = htons(14551);
+
+	/* Bind the socket to port 14551 - necessary to receive packets from qgroundcontrol */ 
+	if (-1 == bind(sock,(struct sockaddr *)&locAddr, sizeof(struct sockaddr)))
+    {
+		perror("error bind failed");
+		close(sock);
+		exit(EXIT_FAILURE);
+    } 
+
+	/* Attempt to make it non blocking */
+	if (fcntl(sock, F_SETFL, O_NONBLOCK | FASYNC) < 0)
+    {
+		fprintf(stderr, "error setting nonblocking: %s\n", strerror(errno));
+		close(sock);
+		exit(EXIT_FAILURE);
+    }
+
+
+	memset(&gcAddr, 0, sizeof(gcAddr));
+	gcAddr.sin_family = AF_INET;
+	gcAddr.sin_addr.s_addr = inet_addr(target_ip);
+	gcAddr.sin_port = htons(14550);
+
+
+
+	for (;;) 
+    {
+
+		/*Send Heartbeat */
+		mavlink_msg_heartbeat_pack(1, 200, &msg, MAV_TYPE_HELICOPTER, MAV_AUTOPILOT_GENERIC, MAV_MODE_GUIDED_ARMED, 0, MAV_STATE_ACTIVE);
+		len = mavlink_msg_to_send_buffer(buf, &msg);
+		bytes_sent = sendto(sock, buf, len, 0, (struct sockaddr*)&gcAddr, sizeof(struct sockaddr_in));
+
+		/* Send Status */
+		mavlink_msg_sys_status_pack(1, 200, &msg, 0, 0, 0, 500, 11000, -1, -1, 0, 0, 0, 0, 0, 0);
+		len = mavlink_msg_to_send_buffer(buf, &msg);
+		bytes_sent = sendto(sock, buf, len, 0, (struct sockaddr*)&gcAddr, sizeof (struct sockaddr_in));
+
+		/* Send Local Position */
+		mavlink_msg_local_position_ned_pack(1, 200, &msg, microsSinceEpoch(), 
+										position[0], position[1], position[2],
+										position[3], position[4], position[5]);
+		len = mavlink_msg_to_send_buffer(buf, &msg);
+		bytes_sent = sendto(sock, buf, len, 0, (struct sockaddr*)&gcAddr, sizeof(struct sockaddr_in));
+
+		/* Send attitude */
+		mavlink_msg_attitude_pack(1, 200, &msg, microsSinceEpoch(), 1.2, 1.7, 3.14, 0.01, 0.02, 0.03);
+		len = mavlink_msg_to_send_buffer(buf, &msg);
+		bytes_sent = sendto(sock, buf, len, 0, (struct sockaddr*)&gcAddr, sizeof(struct sockaddr_in));
+
+
+		memset(buf, 0, BUFFER_LENGTH);
+		recsize = recvfrom(sock, (void *)buf, BUFFER_LENGTH, 0, (struct sockaddr *)&gcAddr, &fromlen);
+		if (recsize > 0)
+      	{
+			// Something received - print out all bytes and parse packet
+			mavlink_message_t msg;
+			mavlink_status_t status;
+
+			printf("Bytes Received: %d\nDatagram: ", (int)recsize);
+			for (i = 0; i < recsize; ++i)
+			{
+				temp = buf[i];
+				printf("%02x ", (unsigned char)temp);
+				if (mavlink_parse_char(MAVLINK_COMM_0, buf[i], &msg, &status))
+				{
+					// Packet received
+					printf("\nReceived packet: SYS: %d, COMP: %d, LEN: %d, MSG ID: %d\n", msg.sysid, msg.compid, msg.len, msg.msgid);
+				}
+			}
+			printf("\n");
+		}
+		memset(buf, 0, BUFFER_LENGTH);
+		sleep(1); // Sleep one second
+    }
+}
+
+
+/* QNX timer version */
+#if (defined __QNX__) | (defined __QNXNTO__)
+uint64_t microsSinceEpoch()
+{
+
+	struct timespec time;
+
+	uint64_t micros = 0;
+
+	clock_gettime(CLOCK_REALTIME, &time);  
+	micros = (uint64_t)time.tv_sec * 100000 + time.tv_nsec/1000;
+
+	return micros;
+}
+#else
+uint64_t microsSinceEpoch()
+{
+
+	struct timeval tv;
+
+	uint64_t micros = 0;
+
+	gettimeofday(&tv, NULL);  
+	micros =  ((uint64_t)tv.tv_sec) * 1000000 + tv.tv_usec;
+
+	return micros;
+}
+#endif