• You have mosquitto-broker running on my windows-PC/pi.
• PLC: “CPU1214C DC/DC/DC” with FW version 4.5 running on TIA v17
• You have successfully tested MQTT connection between PLC and PC by connecting both the hardware through LAN cable 
• This time, you have connected PLC and PC through router. PLC goes online successfully, and you can ping PLC from my PC. But for MQTT communication, when you change “Mqtt.connect” to TRUE, you got error status #7002. Regarding it, you have also referred to siemens document “Libraries for Communication for SIMATIC Controllers” where it told that “status #7002 means Block processes job.”
• Similar question asked here as well, Connect S7-1500 to AWS:16#7002

Solution:

• In my case, I got this error because I have provided the wrong IP-address/FQDN of MQTT-broker. Make sure to double-check it.
• If are trying to connect to public MQTT-broker such as 'test.mosquitto.org', then you may also need to configure "DNS-configuration" in PLC properties where you have to mention "router-ip address" and "google dns address" as well. For more information, you can refer to this document as well