Socket 1 set with data view sring, text data mode, a keepalive time of 30 minutes
and listen auto-response set.
Socket 3 set with data amount sring, hex recv data mode, no keepalive and listen
auto-response not set.
Socket 4 set with hex recv and send data mode.
AT#SCFGEXT?
#SCFGEXT: 1,2,0,30,1,0
#SCFGEXT: 2,0,0,0,0,0
#SCFGEXT: 3,1,1,0,0,0
#SCFGEXT: 4,0,1,0,0,1
...
...
OK