[Update] fix interval delay and update doc

README.md

@@ -18,8 +18,8 @@ Refer to [Azure IoT Edge](https://github.com/Azure/azure-iot-edge)
 
 ## HowTo Run ##
 This section will help you download the prebuilt module image from docker hub, and run it with IoT Edge directly.
-  1. Setup [Azure IoT Edge](https://github.com/Azure/azure-iot-edge) with compatible version on your machine.
+  1. Setup Azure IoT Edge [Windows](https://docs.microsoft.com/en-us/azure/iot-edge/quickstart) or [Linux](https://docs.microsoft.com/en-us/azure/iot-edge/quickstart-linux) with compatible version on your machine.
-  2. Follow [this](https://docs.microsoft.com/en-us/azure/iot-edge/quickstart) to deploy a custom IoT Edge module.
+  2. Follow [this](https://docs.microsoft.com/en-us/azure/iot-edge/tutorial-deploy-modbus-tcp) to deploy a custom IoT Edge module.
   3. In the Image field, enter **microsoft/azureiotedge-modbus-tcp:1.0-preview**.
   4. You may also want to provide configuration to the module when it starts, paste the configuration in the desired property field. For more about configuration, see [here](https://github.com/Azure/iot-edge-modbus#configuration).
 
@@ -27,11 +27,13 @@ This section will help you download the prebuilt module image from docker hub, a
 If you prefer to build your own module, use the following script. Dockerfiles are located under [Docker](https://github.com/Azure/iot-edge-modbus/tree/master/Docker) folder, you should be able to find one for your platform. There are two Dockerfiles in each platform, the multi-stage "Dockerfile-auto" will automatically build source code and Docker image. The other "Dockerfile" requires you to build source code first and then copy binary to the image.  
 **Note**: Arm32 multi-stage build doesn't work at this moment, please build it manually.  
 **Note**: Please replace **PlatForm** in below scripts with the actual platform path you are trying to build.
+
 ### Multi-stage build ###
 ```cmd
 >cd iot-edge-modbus/
 >docker build -t modbusModule -f Docker/<PlatForm>/Dockerfile-auto .
 ```
+
 ### Manually build ###
 The application requires the [.NET Core SDK 2.0](https://www.microsoft.com/net/download/windows).
   ```cmd
@@ -106,18 +108,21 @@ For more about Modbus, please refer to the [Wiki](https://en.wikipedia.org/wiki/
 
 ## Module Endpoints and Routing ##
 All telemetry are sent out from modbusOutput endpoint by default. Routing is enabled by specifying rules like below.
+
 ### Route to IoT Hub ###
 ```json
 {
   "modbusToIoTHub":"FROM /messages/modules/modbus/outputs/modbusOutput INTO $upstream"
 }
 ```
+
 ### Route to other (filter) modules ###
 ```json
 {
   "modbusToFilter":"FROM /messages/modules/modbus/outputs/modbusOutput INTO BrokeredEndpoint(\"/modules/filtermodule/inputs/input1\")"
 }
 ```
+
 ### Write to Modbus ###
 Modbus module also has an input enpoint to receive message/commands. Currently it supports writing back to a single register/cell in a Modbus slave. The content of command must be the following format.
 ```json
@@ -136,5 +141,5 @@ The command should have a property "command-type" with value "ModbusWrite". Also
 ```
 
 ## Debug ##
-There is a flag **IOT_EDGE** at the first line in Program.cs, which can be turn off to debug the Modbus module in console mode. Running console mode requires IoT device connection string being inserted as a environment variable named **EdgeHubConnectionString**, and a local configuration file "iot-edge-modbus.json" since module twin is not available.  
+There is a flag **IOT_EDGE** at the first line in Program.cs, which can be turn off to debug the Modbus module in console mode. Running console mode requires IoT device connection string being inserted as a environment variable named **EdgeHubConnectionString**, and a local configuration file "iot-edge-modbus.json" since module twin is not available. You can copy "iot-edge-modbus.json" template from project root directory.  
 **Note**: running in console mode means none of the IoT Edge features is available. This mode is only to debug non edge-related functions. 

src/ModbusSlave.cs

@@ -55,6 +55,14 @@ namespace Modbus.Slaves
         {
             return ModbusSessionList.Find(x => x.config.HwId.ToUpper() == hwid.ToUpper());
         }
+        public void Release()
+        {
+            foreach (var session in ModbusSessionList)
+            {
+                session.ReleaseSession();
+            }
+            ModbusSessionList.Clear();
+        }
     }
     /// <summary>
     /// Base class of Modbus session.
@@ -65,6 +73,7 @@ namespace Modbus.Slaves
         public abstract Task<List<ModbusOutMessage>> ProcessOperations();
         public abstract Task WriteCB(string uid, string address, string value);
         public abstract Task InitSession();
+        public abstract void ReleaseSession();
     }
     /*
      ----------------------- --------
@@ -92,12 +101,7 @@ namespace Modbus.Slaves
             config = conf;
         }
         #endregion
-        #region Destructors
+
-        ~ModbusTCPSlaveSession()
-        {
-            m_socket.Dispose();
-        }
-        #endregion
         #region Private Properties
         private const int m_reqSize = 12;
         private const int m_bufSize = 512;
@@ -165,6 +169,16 @@ namespace Modbus.Slaves
                 EncodeRead(x);
             }
         }
+
+        public override void ReleaseSession()
+        {
+            if (m_socket != null)
+            {
+                m_socket.Disconnect(false);
+                m_socket.Dispose();
+                m_socket = null;
+            }
+        }
         #endregion
         #region Private Methods
         private async Task ConnectSlave()

src/Program.cs

@@ -181,8 +181,8 @@ namespace Modbus.Containers
 
             try
             {
-                // stop all activities while updating configuration
 #if IOT_EDGE
+                // stop all activities while updating configuration
                 await ioTHubModuleClient.SetInputMessageHandlerAsync(
                 "input1",
                 DummyCallBack,
@@ -229,7 +229,7 @@ namespace Modbus.Containers
         {
             ModuleConfig config;
             Slaves.ModuleHandle moduleHandle;
-            string jsonStr;
+            string jsonStr = null;
             string serializedStr;
 
             serializedStr = JsonConvert.SerializeObject(desiredProperties);
@@ -243,8 +243,19 @@ namespace Modbus.Containers
             }
             else
             {
-                // get config from local file
+                Console.WriteLine("No configuration found in desired properties.");
-                jsonStr = File.ReadAllText(@"..\iot-edge-modbus.json");
+                if (File.Exists(@"iot-edge-modbus.json"))
+                {
+                    try
+                    {
+                        // get config from local file
+                        jsonStr = File.ReadAllText(@"iot-edge-modbus.json");
+                    }
+                    catch (Exception ex)
+                    {
+                        Console.WriteLine("Unable to read configuration from file. Error: " + ex.Message);
+                    }
+                }
             }
 
             if (!string.IsNullOrEmpty(jsonStr))
@@ -263,11 +274,11 @@ namespace Modbus.Containers
                 {
                     var userContext = new Tuple<DeviceClient, Slaves.ModuleHandle>(ioTHubModuleClient, moduleHandle);
 #if IOT_EDGE
-                // Register callback to be called when a message is received by the module
+                    // Register callback to be called when a message is received by the module
-                await ioTHubModuleClient.SetInputMessageHandlerAsync(
+                    await ioTHubModuleClient.SetInputMessageHandlerAsync(
-                "input1",
+                    "input1",
-                PipeMessage,
+                    PipeMessage,
-                userContext);
+                    userContext);
 #else
                     m_task_list.Add(Receive(userContext));
 #endif
@@ -301,11 +312,6 @@ namespace Modbus.Containers
                     var msgs = await s.ProcessOperations();
                     result.AddRange(msgs);
                 }
-                if (!m_run)
-                {
-                    break;
-                }
-                await Task.Delay(m_interval.Interval);
                 if (result.Count > 0)
                 {
                     Message message = new Message(Encoding.ASCII.GetBytes(JsonConvert.SerializeObject(result)));
@@ -316,7 +322,13 @@ namespace Modbus.Containers
                     await ioTHubModuleClient.SendEventAsync(message);
 #endif
                 }
+                if (!m_run)
+                {
+                    break;
+                }
+                await Task.Delay(m_interval.Interval);
             }
+            moduleHandle.Release();
         }
 
         /// <summary>