mqtt下载
https://github.com/eclipse/paho.mqtt.c
makefile需要修改
CC = mipsel-openwrt-linux-gcc
CFLAGS = -I/home/lemon/workspace/openwrt_widora_lemon/staging_dir/target-mipsel_24kec+dsp_uClibc-0.9.33.2/usr/include
LDFLAGS = -L/home/lemon/workspace/openwrt_widora_lemon/staging_dir/target-mipsel_24kec+dsp_uClibc-0.9.33.2/usr/lib