Hi,
I have configured mosquitto server on RasPi and I am using the following 8266 ESP-01 wifi board programmed via the Arduino IDE.
http://www.chinalctech.com/index.php?_m=mod_product&_a=view&p_id=1204
I have it “working” as it joins the WiFi and connects to the mosquitto server.  It subscribes sucessfully to the topic and then receives the commands to open and close the relay.  Up to now I am happy.
Problem is that it uses serial comms between the 8266 and the relay board to instruct on open and close of the relay and this I am having endless problems.  I have not been able to trigger the relay at all.
This should be really simple and I cannot see why I am having so much problems.
Basic code I am using to program the device:
//———————————————————————————
#include <ESP8266WiFi.h>
#include <PubSubClient.h>
const char* ssid = “xxxxxx”;
const char* password = “*******”;
const char* mqttServer = “192.168.8.8”;
const int mqttPort = 1883;
const char* mqttUser = “yyyyyy”;
const char* mqttPassword = “********”;
byte openRelay[] = {0xA0, 0x01, 0x01, 0xA2 }; //A00101A2
byte closeRelay[] = {0xA0, 0x01, 0x00, 0xA1 }; //A00100A1
char* stateDesc = “state-closed”;
bool nowOpen = false;
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {

Serial.begin(9600, SERIAL_8N1);

WiFi.begin(ssid, password);

while (WiFi.status() != WL_CONNECTED) {
delay(500);
}
client.setServer(mqttServer, mqttPort);
client.setCallback(callback);

while (!client.connected()) {
if (!client.connect(“ESP8266Client”, mqttUser, mqttPassword )) {
delay(2000);
}
}

client.publish(“home/esp01”, “state-closed”);
client.subscribe(“home/esp01”);
}

void callback(char* topic, byte* payload, unsigned int length) {

if (length > 0) {
if ((char)payload[0] == ‘0’) {
//Close the valve
delay(1);
Serial.write(closeRelay, sizeof(closeRelay));
/* Serial.write(0xA0);
Serial.write((0x01));
Serial.write((0x00));
Serial.write((0xA1)); */
Serial.flush();
stateDesc = “state-closed”;
nowOpen = false;
client.publish(“home/esp01”, stateDesc);
}
if ((char)payload[0] == ‘1’) {
//Open the valve
delay(1);
Serial.write(openRelay, sizeof(openRelay));
/* Serial.write(0xA0);
Serial.write((0x01));
Serial.write((0x01));
Serial.write((0xA2));*/
Serial.flush();
stateDesc = “state-open”;
nowOpen = true;
client.publish(“home/esp01”, stateDesc);
}
if ((char)payload[0] == ‘2’) {
//Respond with valve status
client.publish(“home/esp01”, stateDesc);
}
}
}

void loop() {
client.loop();
}
//———————————————————————————