[SIL-251] Modbus controller does not reconnect properly in case of

network failure (and sporadic crash)

silecs-communication-cpp/src/silecs-communication/interface/communication/MBConnection.cpp

@@ -26,8 +26,25 @@ namespace Silecs
 
 	MBConnection::MBConnection(PLC* thePLC) : Connection(thePLC)
 	{
-		LOG(ALLOC) << "MBConnection (create): " << thePLC->getName();
-		readCtx_ = writeCtx_ = NULL;
+        LOG(ALLOC) << "MBConnection (create): " << thePLC->getName();
+
+        //Connection use IP address to limit the naming-server accesses
+        readCtx_ = modbus_new_tcp((char *) thePLC->getIPAddress().c_str(), MODBUS_TCP_DEFAULT_PORT /*=502*/);
+        writeCtx_ = modbus_new_tcp((char *) thePLC->getIPAddress().c_str(), MODBUS_TCP_DEFAULT_PORT /*=502*/);
+
+        /*TODO: To be adjusted with the next stable libmodbus release (>3.1.1)
+          which will fix the current timeout response time issue (see libmodbus forum).
+
+        Define Modbus response timeout
+        struct timeval response_timeout;
+        response_timeout.tv_sec = 0;
+        response_timeout.tv_usec = 10000;
+
+        modbus_set_response_timeout(readCtx_ , &response_timeout);
+        modbus_set_response_timeout(writeCtx_ , &response_timeout);
+        */
+
+        //modbus_set_debug(*ctx, TRUE);
 	}
 
 
@@ -35,25 +52,24 @@ namespace Silecs
 	{
 		//Close the connection before removing resources
 		//disable(); must be done before removing resource
+        modbus_free(writeCtx_);
+        modbus_free(readCtx_);
 	}
 
 
 	bool MBConnection::open(PLC* thePLC)
 	{
-		//Open read and write Modbus channels (using IP address to limit the naming-server accesses)
-        int readErr  = IeMdbOpen(&readCtx_, NULL, (char *) thePLC->getIPAddress().c_str(), (int)thePLC->getBaseAddress());
-        int writeErr = IeMdbOpen(&writeCtx_, NULL, (char *) thePLC->getIPAddress().c_str(), (int)thePLC->getBaseAddress());
-        return ((readErr == 0) && (writeErr == 0));
+        int readErr = modbus_connect(readCtx_);
+        int writeErr = modbus_connect(writeCtx_);
+        return ((readErr != -1) && (writeErr != -1));
 	}
 
 
 	bool MBConnection::close(PLC* thePLC)
 	{
-        int err = 0;
-        err |= IeMdbClose(readCtx_);
-        err |= IeMdbClose(writeCtx_);
-        readCtx_ = writeCtx_ = NULL;
-        return (err == 0);
+        modbus_close(readCtx_);
+        modbus_close(writeCtx_);
+        return true;
 	}
 
 

silecs-communication-cpp/src/silecs-communication/protocol/modbus/iemdb.cpp

@@ -109,50 +109,6 @@ double IeMdbGetTime(unsigned char *dt) // from PLC
   return((double)plctm + ms);
 }
 
-/*----------------------------------------------------------*/
-/* This function creates a synchronous OSI-ON-TCP socket
- * channel used for sending/receiving communication with PLC.
- * 'hostName': Name of the host (in)
- * 'plcIP': PLC ip address string (in)
- * return socket descriptor or <0 on error (see const. error)
- *
- * Details:
- * 'plcIP' parameter is necessary only when 'hostName' is NULL.
- * Only one synchronous channel per PLC at the same time
- * supported in that version.
- */
-int IeMdbOpen (modbus_t** ctx, char *hostName, char *plcIP, int baseAddress)
-{
-  *ctx = modbus_new_tcp(plcIP, MODBUS_TCP_DEFAULT_PORT /*=502*/);
-  //modbus_set_debug(*ctx, TRUE);
-
-  if (modbus_connect(*ctx) == -1)
-  {
-      modbus_free(*ctx);
-      return IE_CONNECT_ERROR;
-  }
-
-  return 0;
-}
-
-
-/*----------------------------------------------------------*/
-/* This function closes the synchronous OSI-ON-TCP socket
- * channel.
- * 'sk': socket descriptor (in) - MUST BE a synch. pipe
- * return 0 or <0 on error (see constant error)
- *
- * Details:
- */
-int IeMdbClose(modbus_t* ctx)
-{
-  /* Close the connection */
-  modbus_close(ctx);
-  modbus_free(ctx);
-
-  return 0;
-}
-
 /*----------------------------------------------------------*/
 int IeMBwriteData(modbus_t* ctx, uint16_t start_addr, uint16_t count, uint8_t* data)
 {

silecs-communication-cpp/src/silecs-communication/protocol/modbus/iemdb.h

@@ -36,20 +36,6 @@ void IeMdbSetTime(unsigned char *dt, time_t epoch);  // to PLC
  */
 double IeMdbGetTime(unsigned char *dt); // from PLC
 
-/*----------------------------------------------------------*/
-/* This function creates a synchronous OSI-ON-TCP socket 
- * channel used for sending/receiving communication with PLC.
- * 'hostName': Name of the host (in)
- * 'plcIP': PLC ip address string (in)
- * return socket descriptor or <0 on error (see const. error)
- *
- * Details:
- * 'plcIP' parameter is necessary only when 'hostName' is NULL.
- * Only one synchronous channel per PLC at the same time 
- * supported in that version.
- */
-int IeMdbOpen (modbus_t** ctx, char *hostName, char *plcIP, int baseAddress);
-
 /*----------------------------------------------------------*/
 /* This function send a data segment to the PLC using the
  * MODBUS protocole.
@@ -72,15 +58,5 @@ int IeMBwriteData(modbus_t* ctx, uint16_t dataAddr, uint16_t dataSize, uint8_t*
  */
 int IeMBreadData(modbus_t* ctx, uint16_t dataAddr, uint16_t dataSize, uint8_t* dataBuffer);
 
-/*----------------------------------------------------------*/
-/* This function closes the synchronous OSI-ON-TCP socket 
- * channel.
- * 'cid1': connection id (in) - MUST BE a synch. pipe
- * return 0 or <0 on error (see constant error)
- *
- * Details:
- */
-int IeMdbClose(modbus_t* ctx);
-
 #endif /* _IEMDB_H_ */
 #endif //MODBUS_SUPPORT_ENABLED