Status reporting

MQTT printer connection status message reporting

When the MQTT connection is successful, the terminal will send the following connection information to the MQTT server

{
    "dvsno":"xxx",
    "kind":"DVS",
    "printers":[
        {
            "prtidx":"P01",
            "status":"0200",
            "port":"9100",
            "ieee1284":"MFG:DATONGSMART;MDL:DP320; "
        },
        {
            "prtidx":"P02",
            "status":"0210",
            "port":"9101",
            "ieee1284":""
        },
        {
            "prtidx":"P03",
            "status":"0210",
            "port":"9102",
            "ieee1284":""
        }
    ]
}