ESP8266 and CT sensor on ADC0

TCP/IP is a protocol, not a connector. There is a RJ45 connector on the emonTx, but it is not Ethernet. But you can connect an ESP8266 to the serial output.

The emonTx is sending serial data to the ESP8266, instead of using the radio. The ESP8266 transmits this by WiFi. If the format of the data your ESP8266 generates itself is the same as that which it would receive from the serial output of the emonTx, it should be accepted by emonCMS.