TCP-ESP

ESP8266/ESP32 TCP Examples

Basic client

Client with blocking read operation

Server

API

void client();

Initialize internal structures to act as a Modbus client.

bool connect(IPAddress ip, uint16_t port = MODBUSIP_PORT);
bool disconnect(IPAddress ip);

• ip IP address of the remote Modbus server
• port TCP port of remote Modbus server (standard value is 502)

Note: Just one connection to the specific address is supported. That is the library is unable to simultaniousaly connect to Modbus servers that has same IP address but diffrent ports.

uint16_t readCoil(IPAddress ip, uint16_t offset, bool* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t readCoil(const char* host, uint16_t offset, bool* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t readCoil(String host, uint16_t offset, bool* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t writeCoil(IPAddress ip, uint16_t offset, bool value, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t writeCoil(IPAddress ip, uint16_t offset, bool* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t readIsts(IPAddress ip, uint16_t offset, bool* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t writeHreg(IPAddress ip, uint16_t offset, uint16_t value, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t writeHreg(IPAddress ip, uint16_t offset, uint16_t* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t readHreg(IPAddress ip, uint16_t offset, uint16_t* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);
uint16_t readIreg(IPAddress ip, uint16_t offset, uint16_t* value, uint16_t numregs = 1, cbTransaction cb = nullptr, uint8_t uint = MODBUSIP_UNIT);

• ip IP Address of Modbus server to get registers from
• host Hostname fo Modbus server to get registers from
• offset Address of first Modbus register to read/write
• numregs Count of registers to read/write
• cb Transaction callback function (see Calback examples for details). NULL if not used
• unit Modbus unit

Sends corresponding Modbus read request to Modbus server at ip. Connection with server shoud be already established by connect(ip). Returns transaction id or 0 on failure. Failure maens that client unable to send the request bacause of no connection to the Modbus server is established or other internal error. Note: read/write functions just sending requests to remote Modbus server. The functions returns immediate after request sent and doesn't waiting for result. That is value contains no result data on the function exit. value will be filled as responce arrive and processed by .task() function.

bool isTransaction(uint16_t id);

• id Transaction id.

Returns true if transaction with id is active.

bool isConnected(IPAddress ip);

• ip Remote Modbus server IP address

Returns true is connection with Modbus server at ip is established.

void dropTransactions();

Cancel all active transactions. Callback with result code Modbus::EX_CANCEL will be called for each transaction (if assigned).

Add local register

bool addHreg(uint16_t offset, uint16_t value = 0, uint16_t numregs = 1);
bool addCoil(uint16_t offset, bool value = false, uint16_t numregs = 1);
bool addIsts(uint16_t offset, bool value = false, uint16_t numregs = 1);
bool addIreg(uint16_t offset, uint16_t value = 0, uint16_t nemregs = 1);

• offset Address of the first register to add
• value Initial value to be assigned to register(s)
• numregs Count of registers to be created

Adding new register(s) and assigning value(s). If [some] registers already exists value will be updated. Returns true on success. false if operation is failed for some reason.

Write local reg

bool Hreg(uint16_t offset, uint16_t value);
bool Coil(uint16_t offset, bool value);
bool Ists(uint16_t offset, bool value);
bool Ireg(uint16_t offset, uint16_t value);

• offset Address of the register
• value Value to be assigned to register

Returns true on success. false if register not previousely added or other error.

Read local reg

uint16_t Hreg(uint16_t offset);
bool Coil(uint16_t offset);
bool Ists(uint16_t offset);
uint16_t Ireg(uint16_t offset);

• offset Address of the register to read

Returns current value of the register.

Remove reg(s)

bool removeHreg(uint16_t offset, uint16_t numregs = 1);
bool removeCoil(uint16_t offset, uint16_t numregs = 1);
bool removeIsts(uint16_t offset, uint16_t numregs = 1);
bool removeIreg(uint16_t offset, uint16_t numregs = 1);

• offset Address of the first register to remove
• numregs Count of registers to be created

Function trying to remove numregs registers starting from offset. If some of registers within the range are not exists removal continues execution. Returns true if atleast one register in the range was removed.

Modbus Library for Arduino

ModbusRTU, ModbusTCP and ModbusTCP Security

(c)2020 Alexander Emelianov

The code in this repo is licensed under the BSD New License. See LICENSE.txt for more info.