错误：datatype/md5sum
学习中科院ros入门时，在用roscpp实现主题的发布和订阅，遇到以下错误：[ERROR] : Client [/listener] wants topic /gps_info to have datatype/md5sum [topic_demo/gps/21b595b2539ba75170061ab15234e4eb], but our version has [topic_demo/gp...
