我的 AT 命令：
AT+CREG?
AT+SAPBR=3,1,"Contype","GPRS"
AT+SAPBR=3,1,"APN","mtnirancell"
AT+SAPBR=3,1,"USER","xxxx"
AT+SAPBR=3,1,"PWD","xxxxx"
AT+SAPBR=1,1
AT+FTPCID=1
AT+FTPSERV="yzd.ir"
AT+FTPPORT=21
AT+FTPUN="xxxx"
AT+FTPPW="xxxx"
AT+FTPPUTNAME="ehsan.txt"
AT+FTPPUTPATH="/"
AT+FTPPUT=1
AT+FTPPUT=2,10
服务器日志：
Jul 21 13:42:36 yzd proftpd[2019] yzd (::ffff:5.116.194.141[::ffff:5.116.194.141]): FTP session opened.
Jul 21 13:42:36 yzd proftpd[2019] yzd (::ffff:5.116.194.141[::ffff:5.116.194.141]): USER xxxx: Login successful.
Jul 21 13:42:38 yzd proftpd[2019] yzd (::ffff:5.116.194.141[::ffff:5.116.194.141]): FTP session closed.