Merge pull request #177 from yaacov/add-async-server-example

add a server example

README.md

@@ -146,7 +146,7 @@ const getMetersValue = async (meters) => {
 }
 
 const getMeterValue = async (id) => {
-    try {	
+    try {
         // set ID of slave
         await client.setID(id);
         // read the 1 registers starting at address 0 (first register)
@@ -156,7 +156,7 @@ const getMeterValue = async (id) => {
     } catch(e){
         // if error return -1
         return -1
-    } 
+    }
 }
 
 const sleep = (ms) => new Promise(resolve => setTimeout(resolve, ms));
@@ -217,7 +217,8 @@ var vector = {
     getHoldingRegister: function(addr, unitID, callback) {
         // Asynchronous handling (with callback)
         setTimeout(function() {
-            callback(addr + 8000);
+            // callback = function(err, value)
+            callback(null, addr + 8000);
         }, 10);
     },
     getCoil: function(addr, unitID) {

examples/async_server.js

@@ -0,0 +1,50 @@
+/* eslint-disable no-console, no-unused-vars, spaced-comment */
+
+// create an empty modbus client
+//var ModbusRTU = require("modbus-serial");
+var ModbusRTU = require("../index");
+var vector = {
+    getInputRegister: function(addr, unitID) {
+        // Synchronous handling
+        return addr;
+    },
+    getHoldingRegister: function(addr, unitID, callback) {
+        // Asynchronous handling (with callback)
+        setTimeout(function() {
+            // callback = function(err, value)
+            callback(null, addr + 8000);
+        }, 10);
+    },
+    getCoil: function(addr, unitID) {
+        // Asynchronous handling (with Promises, async/await supported)
+        return new Promise(function(resolve) {
+            setTimeout(function() {
+                resolve(addr % 2 === 0);
+            }, 10);
+        });
+    },
+    setRegister: function(addr, value, unitID) {
+        // Asynchronous handling supported also here
+        console.log("set register", addr, value, unitID);
+        return;
+    },
+    setCoil: function(addr, value, unitID) {
+        // Asynchronous handling supported also here
+        console.log("set coil", addr, value, unitID);
+        return;
+    }
+};
+
+// set the server to answer for modbus requests
+console.log("ModbusTCP listening on modbus://0.0.0.0:8502");
+var serverTCP = new ModbusRTU.ServerTCP(vector, {
+    host: "0.0.0.0",
+    port: 8502,
+    debug: true,
+    unitID: 1
+});
+
+serverTCP.on("socketError", function(err) {
+    // Handle socket error if needed, can be ignored
+    console.error(err);
+});