关于rcS文件的UDP端口

可见仿真的时候PX4和gazebo之间的通信是两个进程通过UDP 端口通信，自己写过UDP通信之后这就好理解了。

没有自己弄个TCP UDP通信的这一时半会可能就不好理解。

地面站连飞控，是地面站端填IP，地面站端应该是客户端主动发起连接，飞控这边是服务端，等待连，那么写和地面站的UDP连接的时候，我们这边应该是写成服务端，现在应该清楚了！！！！

既然是通过UDP端口，PX4讲道理不放在本机上也是可以的啊，清楚了这个本质你就可以任意自由更改了。或许这也是为什么QGC放在docker外部也可以连上PX4的原因。

我突然看到这个init.d-posix就更有感触了，posix。

https://gitee.com/maxibooksiyi/prometheus_px4/blob/Prometheus_PX4_1.11.1/ROMFS/px4fmu_common/init.d-posix/rcS

#!/bin/sh

# PX4 commands need the 'px4-' prefix in bash.
# (px4-alias.sh is expected to be in the PATH)
# shellcheck disable=SC1091
. px4-alias.sh

SCRIPT_DIR="$(CDPATH='' cd -- "$(dirname -- "$0")" && pwd)"

#
# Main SITL startup script
#

# check for ekf2 replay
# shellcheck disable=SC2154
if [ "$replay_mode" = "ekf2" ]
then
	sh etc/init.d-posix/rc.replay
	exit 0
fi

# initialize script variables
set AUX_MODE                    none
set IO_PRESENT                  no
set LOG_FILE                    bootlog.txt
set MAV_TYPE                    none
set MIXER                       none
set MIXER_AUX                   none
set MIXER_FILE                  none
set OUTPUT_MODE                 sim
set PWM_OUT                     none
set SDCARD_MIXERS_PATH          etc/mixers
set USE_IO                      no
set VEHICLE_TYPE                none
set LOGGER_ARGS                 ""
set LOGGER_BUF                  1000

set RUN_MINIMAL_SHELL           no

# Use the variable set by sitl_run.sh to choose the model settings.
if [ "$PX4_SIM_MODEL" = "shell" ]; then
	set RUN_MINIMAL_SHELL yes
else
	# Find the matching Autostart ID (file name has the form: [0-9]+_${PX4_SIM_MODEL})
	# TODO: unify with rc.autostart generation
	# shellcheck disable=SC2012
	REQUESTED_AUTOSTART=$(ls "$SCRIPT_DIR" | sed -n 's/^\([0-9][0-9]*\)_'${PX4_SIM_MODEL}'$/\1/p')
	if [ -z "$REQUESTED_AUTOSTART" ]; then
		echo "Error: Unknown model '$PX4_SIM_MODEL'"
		exit 1
	fi
fi

# clear bootlog
[ -f $LOG_FILE ] && rm $LOG_FILE


uorb start

# Load parameters
set PARAM_FILE eeprom/parameters_"$REQUESTED_AUTOSTART"
param select $PARAM_FILE

if [ -f $PARAM_FILE ]
then
	if param load
	then
		echo "[param] Loaded: $PARAM_FILE"
	else
		echo "[param] FAILED loading $PARAM_FILE"
	fi
else
	echo "[param] parameter file not found, creating $PARAM_FILE"
fi

# exit early when the minimal shell is requested
[ $RUN_MINIMAL_SHELL = yes ] && exit 0


# Use environment variable PX4_ESTIMATOR to choose estimator.
if [ "$PX4_ESTIMATOR" = "q" ]; then
	param set SYS_MC_EST_GROUP 3
elif [ "$PX4_ESTIMATOR" = "ekf2_gps" ]; then
	param set SYS_MC_EST_GROUP 2
	param set EKF2_AID_MASK 1
	param set EKF2_HGT_MODE 0
elif [ "$PX4_ESTIMATOR" = "ekf2_vision" ]; then
	param set SYS_MC_EST_GROUP 2
	param set EKF2_AID_MASK 24
	param set EKF2_EV_DELAY 5
	param set EKF2_HGT_MODE 3
elif [ "$PX4_ESTIMATOR" = "inav" ]; then
	param set SYS_MC_EST_GROUP 0
fi


if param compare SYS_AUTOSTART $REQUESTED_AUTOSTART
then
	set AUTOCNF no
else
	set AUTOCNF yes
	param set SYS_AUTOCONFIG 1
fi

if param compare SYS_AUTOCONFIG 1
then
	set AUTOCNF yes

	# Wipe out params except RC*, flight modes, total flight time, accel cal, gyro cal, next flight UUID
	param reset_nostart RC* COM_FLTMODE* LND_FLIGHT_T_* TC_* CAL_ACC* CAL_GYRO* COM_FLIGHT_UUID
fi

# multi-instance setup
# shellcheck disable=SC2154
param set MAV_SYS_ID $((px4_instance+1))
simulator_tcp_port=$((4560+px4_instance))
udp_offboard_port_local=$((14580+px4_instance))
udp_offboard_port_remote=$((14540+px4_instance))
[ $px4_instance -gt 9 ] && udp_offboard_port_remote=14549 # use the same ports for more than 10 instances to avoid port overlaps
udp_onboard_payload_port_local=$((14280+px4_instance))
udp_onboard_payload_port_remote=$((14030+px4_instance))
udp_gcs_port_local=$((18570+px4_instance))

if [ $AUTOCNF = yes ]
then
	param set SYS_AUTOSTART $REQUESTED_AUTOSTART

	param set BAT_N_CELLS 4

	param set CAL_ACC0_ID 1311244
	param set CAL_ACC_PRIME 1311244

	param set CAL_GYRO0_ID 1311244
	param set CAL_GYRO_PRIME 1311244

	param set CAL_MAG0_ID 197388
	param set CAL_MAG_PRIME 197388

	param set CBRK_AIRSPD_CHK 0
	param set CBRK_SUPPLY_CHK 894281

	# Don't require RC calibration and configuration
	param set COM_RC_IN_MODE 1

	param set EKF2_ANGERR_INIT 0.01
	param set EKF2_GBIAS_INIT 0.01

	# Prevent high accel bias
	param set COM_ARM_EKF_AB 0.005

	# Speedup SITL startup
	param set EKF2_REQ_GPS_H 0.5

	# LPE: GPS only mode
	param set LPE_FUSION 145

	param set MC_PITCH_P 6
	param set MC_PITCHRATE_P 0.2
	param set MC_ROLL_P 6
	param set MC_ROLLRATE_P 0.2

	param set MPC_Z_VEL_P_ACC 12.0
	param set MPC_Z_VEL_I_ACC 3.0
	param set MPC_XY_P 0.8
	param set MPC_XY_VEL_P_ACC 4.0
	param set MPC_XY_VEL_I_ACC 0.4
	param set MPC_XY_VEL_D_ACC 0.32

	param set RTL_RETURN_ALT 30

	# By default log from boot until first disarm.
	param set SDLOG_MODE 1
	# enable default, estimator replay and vision/avoidance logging profiles
	param set SDLOG_PROFILE 131
	param set SDLOG_DIRS_MAX 7
	param set SENS_BOARD_ROT 0
	param set SENS_BOARD_X_OFF 0.000001
	param set SENS_DPRES_OFF 0.001
	param set SYS_RESTART_TYPE 2

	param set TRIG_INTERFACE 3
fi

param set COM_CPU_MAX -1 # disable check, no CPU load reported on posix yet

# Simulator IMU data provided at 250 Hz
param set IMU_INTEG_RATE 250

# Adapt timeout parameters if simulation runs faster or slower than realtime.
if [ -n "$PX4_SIM_SPEED_FACTOR" ]; then
	COM_DL_LOSS_T_LONGER=$(echo "$PX4_SIM_SPEED_FACTOR * 10" | bc)
	echo "COM_DL_LOSS_T set to $COM_DL_LOSS_T_LONGER"
	param set COM_DL_LOSS_T $COM_DL_LOSS_T_LONGER

	COM_RC_LOSS_T_LONGER=$(echo "$PX4_SIM_SPEED_FACTOR * 0.5" | bc)
	echo "COM_RC_LOSS_T set to $COM_RC_LOSS_T_LONGER"
	param set COM_RC_LOSS_T $COM_RC_LOSS_T_LONGER

	COM_OF_LOSS_T_LONGER=$(echo "$PX4_SIM_SPEED_FACTOR * 0.5" | bc)
	echo "COM_OF_LOSS_T set to $COM_OF_LOSS_T_LONGER"
	param set COM_OF_LOSS_T $COM_OF_LOSS_T_LONGER
fi

# Autostart ID
autostart_file=''
for f in etc/init.d-posix/"$(param show -q SYS_AUTOSTART)"_*
do
	filename=$(basename "$f")
	case "$filename" in
		*\.*)
			# ignore files that contain a dot (e.g. <vehicle>.post)
			;;
		*)
			autostart_file="$f"
			;;
	esac
done
if [ ! -e "$autostart_file" ]; then
	echo "Error: no autostart file found ($autostart_file)"
	exit 1
fi

sh "$autostart_file"

#
# If autoconfig parameter was set, reset it and save parameters.
#
if [ $AUTOCNF = yes ]
then
	param set SYS_AUTOCONFIG 0
fi

dataman start
# only start the simulator if not in replay mode, as both control the lockstep time
if ! replay tryapplyparams
then
	simulator start -c $simulator_tcp_port
fi
battery_simulator start
tone_alarm start
rc_update start
sensors start
commander start
navigator start


if ! param compare -s MNT_MODE_IN -1
then
	vmount start
fi

if param greater -s TRIG_MODE 0
then
	camera_trigger start
	camera_feedback start
fi

# Configure vehicle type specific parameters.
# Note: rc.vehicle_setup is the entry point for rc.interface,
#       rc.fw_apps, rc.mc_apps, rc.rover_apps, and rc.vtol_apps.
#
sh etc/init.d/rc.vehicle_setup

# GCS link
mavlink start -x -u $udp_gcs_port_local -r 4000000
mavlink stream -r 50 -s POSITION_TARGET_LOCAL_NED -u $udp_gcs_port_local
mavlink stream -r 50 -s LOCAL_POSITION_NED -u $udp_gcs_port_local
mavlink stream -r 50 -s GLOBAL_POSITION_INT -u $udp_gcs_port_local
mavlink stream -r 50 -s ATTITUDE -u $udp_gcs_port_local
mavlink stream -r 50 -s ATTITUDE_QUATERNION -u $udp_gcs_port_local
mavlink stream -r 50 -s ATTITUDE_TARGET -u $udp_gcs_port_local
mavlink stream -r 50 -s SERVO_OUTPUT_RAW_0 -u $udp_gcs_port_local
mavlink stream -r 20 -s RC_CHANNELS -u $udp_gcs_port_local
mavlink stream -r 10 -s OPTICAL_FLOW_RAD -u $udp_gcs_port_local

# API/Offboard link
mavlink start -x -u $udp_offboard_port_local -r 4000000 -m onboard -o $udp_offboard_port_remote

# Onboard link to camera
mavlink start -x -u $udp_onboard_payload_port_local -r 4000 -f -m onboard -o $udp_onboard_payload_port_remote

# execute autostart post script if any
[ -e "$autostart_file".post ] && sh "$autostart_file".post

# Run script to start logging
if param compare SYS_MC_EST_GROUP 2
then
	set LOGGER_ARGS "-p ekf2_timestamps"
else
	set LOGGER_ARGS "-p vehicle_attitude"
fi
sh etc/init.d/rc.logging

mavlink boot_complete
replay trystart

 http://blog.sina.cn/dpool/blog/s/blog_aa9fb81a0102wbbe.html

 似乎PX4启动去跑的第一个文件就是rcS文件？