This post reports how to use java to communicate with slaves via Modbus TCP。
项目需求
最近做一个项目需要和各种主流工业协议通讯，而且要求可以添加特定协议的各类设备。添加完设备后还需要我们和该设备针剂通过协议读取数据和控制。其中Modbus是最主要的协议之一。
该项目对灵活性和通用型要求非常高，对我们的设计自然是复杂度也比较难，后续我会讲述如何设计的。这里我主要讲述如何通过jamod(Java Modbus Library) 库在JAVA环境下与Modbus TCP 和RTU通信的。源码下载地址
测试环境
虽然我们要求与实际设备联动，但在开发阶段我想模拟出多个Modbus测试环境，网上搜索后发现modbustools提供的Master和Slave工具非常不错，
modbustools，可以根据自己的需求下载相关的模拟器，这里我首先要模拟一个modbus设备，所以下载了Slave端程序。我的开发环境是windows，现在安装后根据需求配置slave即可。
无奈没有注册码只能试用三十天。 绿色版下载地址
modbustools slave 协议选择
modbustools slave 客户端配置
Modbus 分析
Supported Modbus Functions:
- 01: Read coil status
- 02: Read input status
- 03: Read holding registers
- 04: Read input registers
- 05: Force single coil
- 06: Preset single register
- 15: Force multiple coils
- 16: Preset multiple registers
以读数据为例个人的理解就是:
- 01 可以读写的布尔类型
- 02 只能读的布尔类型
- 03 只能读的数字类型
- 04 可以读写的数字类型
jamod也提供了操作每种不同类型使用不同的类，这里给出个表格。
| 功能 | 请求类 | 响应类 |
| 01 只能读的布尔类型 | ReadCoilsRequest | ReadCoilsResponse |
| 02 可以读写的布尔类型 | ReadInputDiscretesRequest | ReadInputDiscretesResponse |
| 03 只能读的数字类型 | ReadMultipleRegistersRequest | ReadMultipleRegistersResponse |
| 04 可以读写的布尔类型 | ReadInputRegistersRequest | ReadInputRegistersResponse |
代码分析
Talk is cheap, 直接整代码
F01 读取Coill类型数据
这里需要的参数分别是 Ip地址 端口号，参数地址，设备地址. 在这里我们只读取一位数据，所以默认数据长度设置为1，在实际中也可以给多位，则要修改返回数据列表处理时。
ReadCoilsRequest req = new ReadCoilsRequest(ref, count); 这里count给的是1
代码如下
public static int readDiscretesInput(String ip, int port, int ref, int slaveId) {
int data = 0;
try {
InetAddress addr = InetAddress.getByName(ip);
// 1 build the connection with ip and port
TCPMasterConnection con = ModbusConnection.openTcpConnection(ip, port);
// 2 the 1st: the ref of register; 2nd is the number of register will be read
ReadCoilsRequest req = new ReadCoilsRequest(ref, 1);
// 3 set the Slave Id (deviceId)
req.setUnitID(slaveId);
// 4 open a transaction and set the request params
ModbusTCPTransaction trans = new ModbusTCPTransaction(con);
trans.setRequest(req);
// 5 execute the search
trans.execute();
// 6 get the result
ReadCoilsResponse res = ((ReadCoilsResponse) trans.getResponse());
if(res.getDiscretes().getBit(0)){
data = 1;
}
// 7 close the connection
con.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
F02 读取DiscretesInput类型数据
public static int readDiscretesInput(String ip, int port, int ref, int slaveId) {
int data = 0;
try {
InetAddress addr = InetAddress.getByName(ip);
// build the connection
TCPMasterConnection con = ModbusConnection.openTcpConnection(ip, port);
// the 1st: the ref of register; 2nd is the number of register will be read
ReadInputDiscretesRequest req = new ReadInputDiscretesRequest(ref, 1);
// the Slave Id
req.setUnitID(slaveId);
ModbusTCPTransaction trans = new ModbusTCPTransaction(con);
trans.setRequest(req);
// execute the search
trans.execute();
// get the result
ReadInputDiscretesResponse res = (ReadInputDiscretesResponse) trans.getResponse();
if(res.getDiscretes().getBit(0)){
data = 1;
}
// 关闭连接
con.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
F03 读取HoldingRegister类型数据
public static int readRegister(String ip, int port, int ref,
int slaveId) {
int data = 0;
try {
TCPMasterConnection con = ModbusConnection.openTcpConnection(ip, port);
con.connect();
ReadMultipleRegistersRequest req = new ReadMultipleRegistersRequest(ref, 1);
req.setUnitID(slaveId);
ModbusTCPTransaction trans = new ModbusTCPTransaction(con);
trans.setRequest(req);
trans.execute();
ReadMultipleRegistersResponse res = (ReadMultipleRegistersResponse) trans.getResponse();
data = res.getRegisterValue(0);
con.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
F04 读取InputRegister类型数据
public static int readRegister(String ip, int port, int ref,
int slaveId) {
int data = 0;
try {
TCPMasterConnection con = ModbusConnection.openTcpConnection(ip, port);
con.connect();
ReadMultipleRegistersRequest req = new ReadMultipleRegistersRequest(ref, 1);
req.setUnitID(slaveId);
ModbusTCPTransaction trans = new ModbusTCPTransaction(con);
trans.setRequest(req);
trans.execute();
ReadMultipleRegistersResponse res = (ReadMultipleRegistersResponse) trans.getResponse();
data = res.getRegisterValue(0);
con.close();
} catch (Exception e) {
e.printStackTrace();
}
return data;
}
F05 写Discretes Coil 类型数据
public static void writeDigitalOutput(String ip, int port, int slaveId,
int ref, int value) {
try {
TCPMasterConnection connection = ModbusConnection.openTcpConnection(ip, port);
connection.connect();
ModbusTCPTransaction trans = new ModbusTCPTransaction(connection);
boolean val = true;
if (value == 0) {
val = false;
}
WriteCoilRequest req = new WriteCoilRequest(ref, val);
req.setUnitID(slaveId);
trans.setRequest(req);
System.out.println("ModbusSlave: FC" + req.getFunctionCode()
+ " ref=" + req.getReference() + " value="
+ val);
trans.execute();
connection.close();
} catch (Exception ex) {
System.out.println("writeDigitalOutput Error in code");
ex.printStackTrace();
}
}
F06 写Input Register 类型数据
public static void writeRegister(String ip, int port, int slaveId,
int ref, int value) {
try {
TCPMasterConnection connection = ModbusConnection.openTcpConnection(ip, port);
connection.connect();
ModbusTCPTransaction trans = new ModbusTCPTransaction(connection);
SimpleRegister register = new SimpleRegister(value);
WriteSingleRegisterRequest req = new WriteSingleRegisterRequest(
ref, register);
req.setUnitID(slaveId);
trans.setRequest(req);
System.out.println("ModbusSlave: FC" + req.getFunctionCode()
+ " ref=" + req.getReference() + " value="
+ register.getValue());
trans.execute();
connection.close();
} catch (Exception ex) {
System.out.println("Error in code");
ex.printStackTrace();
}
}
程序测试
测试环境客户端配合
测试结果
配置完成模拟器，即可测试读写各类型数据。测试结果如下：
总结
本文成功测试了Modbus TCP的六种functions的读写。 所有源代码都在github上， 欢迎关注，欢迎讨论。
源码地址 https://github.com/freerambo/jamod.git
接下来我将讲述如何用jamod实现modbust RTU的通信。