Limit incoming connections to one per IP

Author: emelianov

README.md

@@ -70,16 +70,17 @@ http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf
 + added read/write/push/pullCoil/Hreg/Ireg/Ists() parameter to specify Modbus unit id
 + added ability to auto connect to slave. Setting is global. Disabled by default.
 // 2.0.1
-+ Fix readCoil\Hreg\Ists\Ireg not read value from slave
++ Master. Fix readCoil\Hreg\Ists\Ireg not read value from slave
 + Fix crash on disconnect with Arduino Core 2.5.x
 // 2.1.0
-+ Fix slave error response on write multiple Hregs\Coils
-+ Fix writeCoil() for multiple coils
-+ dropTransactions()
-+ disconnect()
++ Slave. Fix error response on write multiple Hregs\Coils
++ Slave. Fix writeCoil() for multiple coils
++ Master. dropTransactions()
++ Master. disconnect()
 + ~ModbusIP()
 + task() cleanup
 + Modify examples
++ Slave. Allow only single incoming master connection per IP
 // 2.2.0
 - code cleanup
 - Implement Private Reg/Coil

src/ModbusIP_ESP8266.cpp

@@ -57,6 +57,15 @@ void ModbusIP::task() {
 			if (!currentClient || !currentClient->connected())
 				continue;
 			if (cbConnect == nullptr || cbConnect(currentClient->remoteIP())) {
+				#ifdef MODBUSIP_UNIQUE_CLIENTS
+				n = getMaster(currentClient->remoteIP());
+				if (n != -1) {
+					client[n]->flush();
+					client[n]->stop();
+					delete client[n];
+					client[n] = nullptr;
+				}
+				#endif
 				n = getFreeClient();
 				if (n > -1) {
 					client[n] = currentClient;
@@ -154,7 +163,7 @@ void ModbusIP::task() {
 uint16_t ModbusIP::send(IPAddress ip, TAddress startreg, cbTransaction cb, uint8_t unit, void* data, bool waitResponse) {
 	MBAP_t _MBAP;
 #ifdef MODBUSIP_MAX_TRANSACIONS
-	if (this->_trans.size() >= MODBUSIP_MAX_TRANSACIONS) return false;
+	if (_trans.size() >= MODBUSIP_MAX_TRANSACIONS) return false;
 #endif
 	int8_t p = getSlave(ip);
 	if (p == -1 || !client[p]->connected())

src/ModbusIP_ESP8266.h

@@ -19,6 +19,7 @@
 #define MODBUSIP_MAX_TRANSACIONS 16
 #define MODBUSIP_MAX_CLIENTS	  4
 #define MODBUSIP_ADD_REG  1
+#define MODBUSIP_UNIQUE_CLIENTS
 
 // Callback function Type
 typedef bool (*cbModbusConnect)(IPAddress ip);