STM32 Ethernet and simular workaround #278

Author: emelianov

src/ModbusSettings.h

@@ -61,6 +61,7 @@ If defined regisers count will be limited.
 #define MODBUS_MAX_FILES 0x270F
 #define MODBUSTCP_PORT 	  502
 #define MODBUSTLS_PORT 	  802
+#define MODBUSIP_MINFRAME 2
 #define MODBUSIP_MAXFRAME 200
 
 /*
@@ -82,6 +83,14 @@ ESP32 only. Outgoing connection attempt timeout
 #endif
 #define MODBUSIP_UNIQUE_CLIENTS
 #define MODBUSIP_MAX_READMS 100
+
+/*
+Use available() instead of accept() to get TCP client
+#define MODBUSIP_USE_AVAILABLE
+Used to wrap variation in Ethernet/WiFi client API implementations
+*/
+//#define MODBUSIP_USE_AVAILABLE
+
 #define MODBUSIP_FULL
 //#define MODBUSIP_DEBUG
 /*

src/ModbusTCPTemplate.h

@@ -214,7 +214,11 @@ void ModbusTCPTemplate<SERVER, CLIENT>::task() {
 		CLIENT c;
 		// WiFiServer.available() == Ethernet.accept() and should wrapped to get code to be compatible with Ethernet library (See ModbusTCP.h code).
 		// WiFiServer.available() != Ethernet.available() internally
+#if defined(MODBUSIP_USE_AVAILABLE)
+		while (millis() - taskStart < MODBUSIP_MAX_READMS && (c = tcpserver->available())) {
+#else
 		while (millis() - taskStart < MODBUSIP_MAX_READMS && (c = tcpserver->accept())) {
+#endif
 #if defined(MODBUSIP_DEBUG)
 			Serial.println("IP: Accepted");
 #endif
@@ -244,7 +248,11 @@ void ModbusTCPTemplate<SERVER, CLIENT>::task() {
 					Serial.print("IP: Conn ");
 					Serial.println(n);
 #endif
+#if defined(MODBUSIP_USE_AVAILABLE)
+					break;	// while
+#else
 					continue; // while
+#endif
 				}
 			}
 			// Close connection if callback returns false or MODBUSIP_MAX_CLIENTS reached
@@ -268,14 +276,15 @@ void ModbusTCPTemplate<SERVER, CLIENT>::task() {
 				continue;
 			}
 			_len = __swap_16(_MBAP.length);
-			if (_len < MODBUSIP_MINFRAME) {	// Length is over MODBUSIP_MAXFRAME
+			if (_len < MODBUSIP_MINFRAME) {	// Length is shorter than MODBUSIP_MINFRAME
+				Modbus::FunctionCode fc = FC_READ_COILS; // Just placeholder
 				while (tcpclient[n]->available())	// Drop rest of the packet
 					tcpclient[n]->read();
 				exceptionResponse(fc, EX_ILLEGAL_VALUE);
 			}
 			_len--; // Do not count with last byte from MBAP
 			if (_len > MODBUSIP_MAXFRAME) {	// Length is over MODBUSIP_MAXFRAME
-			    Modbus::FunctionCode fc = tcpclient[n]->read();
+			    Modbus::FunctionCode fc = (Modbus::FunctionCode)tcpclient[n]->read();
 				_len--;	// Subtract for read byte
 				for (uint8_t i = 0; tcpclient[n]->available() && i < _len; i++)	// Drop rest of the packet
 					tcpclient[n]->read();
@@ -285,15 +294,15 @@ void ModbusTCPTemplate<SERVER, CLIENT>::task() {
 				free(_frame);
 				_frame = (uint8_t*) malloc(_len);
 				if (!_frame) {
-			    	Modbus::FunctionCode fc = tcpclient[n]->read();
+			    	Modbus::FunctionCode fc = (Modbus::FunctionCode)tcpclient[n]->read();
 					_len--;	// Subtract for read byte
 					for (uint8_t i = 0; tcpclient[n]->available() && i < _len; i++)	// Drop rest of the packet
 						tcpclient[n]->read();
 					exceptionResponse(fc, EX_SLAVE_FAILURE);
 				}
 				else {
 					if (tcpclient[n]->readBytes(_frame, _len) < _len) {	// Try to read MODBUS frame
-						exceptionResponse((FunctionCode)_frame[0], EX_ILLEGAL_VALUE);
+						exceptionResponse((Modbus::FunctionCode)_frame[0], EX_ILLEGAL_VALUE);
 						//while (tcpclient[n]->available())	// Drop all incoming (if any)
 						//	tcpclient[n]->read();
 					}