This is a Mqtt broker for embedded devices, developed in C++, FreeRTOS to use advanced multitasking capabilities, and arduino core. Tested in an Esp32 and esp8266.
AT+CSQ
+CSQ: 27,99
OK
AT+CPIN?
+CPIN: READY
OK
AT+CPSI?
+CPSI: LTE,Online,214-03,0x2526,248405103,497,EUTRAN-BAND3,1849,5,0,8,50,55,10
OK
AT+CMQTTSTART
OK
+CMQTTSTART: 0
AT+CMQTTACCQ=0,"a1accq",0
OK
AT+CMQTTCFG="argtopic",0,1,1
OK
AT+CMQTTCONNECT=0,"tcp://192.168.43.128:1883",20,1
+CMQTTCONNECT: 0,3
ERROR
AT+CMQTTCONNECT=0,"tcp://192.168.43.128",20,1
+CMQTTCONNECT: 0,3
ERROR
Using SSCOM tool: