java - Jamod的Modbus/TCP

我编写了以下程序，以了解如何使用jamod访问寄存器。首先，我使用“ Modbus从站”来模拟虚拟TCP-MODBUS保持寄存器。我将程序与jamod lib一起使用，以读取刚刚创建的保持寄存器。

但是我有下面的错误：

Exception in thread "main" java.lang.Error: Unresolved compilation problem:
        MAX_IP_MESSAGE_LENGTH cannot be resolved or is not a field
        at net.wimpi.modbus.io.ModbusTCPTransport.prepareStreams(ModbusTCPTransport.java:223)
        at net.wimpi.modbus.io.ModbusTCPTransport.setSocket(ModbusTCPTransport.java:79)
        at net.wimpi.modbus.io.ModbusTCPTransport.<init>(ModbusTCPTransport.java:59)
        at net.wimpi.modbus.net.TCPMasterConnection.prepareTransport(TCPMasterConnection.java:104)
        at net.wimpi.modbus.net.TCPMasterConnection.connect(TCPMasterConnection.java:67)
        at test_modbus.main(test_modbus.java:36)

这是我的程序

import java.io.*;
import java.lang.*;
import java.net.InetAddress;
import net.wimpi.modbus.Modbus;
import net.wimpi.modbus.io.ModbusTCPTransaction;
import net.wimpi.modbus.msg.WriteCoilRequest;
import net.wimpi.modbus.msg.ReadInputRegistersRequest;
import net.wimpi.modbus.msg.ReadInputRegistersResponse ;
import net.wimpi.modbus.net.TCPMasterConnection;

public class test_modbus {

    public static void main(String args[]) {
        try {
            /* The important instances of the class */
            TCPMasterConnection con = null; // the connection
            ModbusTCPTransaction trans = null; // the transaction
            ReadInputRegistersRequest rreq = null; // the read request
            ReadInputRegistersResponse  rres = null; // the read response
            WriteCoilRequest req = null; // the write request


            /* Variables for storing the parameters */
            InetAddress addr = null; // the slave's address
            int port = 502; // the default port


            // 1. Setup the parameters
            addr = InetAddress.getByName("127.0.0.1"); // ** The address
                                                            // assigned to the
                                                            // module **

            // 2. Open the connection
            con = new TCPMasterConnection(addr);
            con.setPort(port);
            con.connect();
            System.out.println( "--- Message: Line:36 success --- " );
            // ~~~~~~~~~~~~~~~~~~~~ The faulty Read Request ~~~~~~~~~~~~~~~~~~~~
            // 3r. Prepare the READ request
            int k = 4000;
            rreq = new ReadInputRegistersRequest(k, 2); // Reading 8 bytes (of
                                                        // what??)

            // 4r. Prepare the READ transaction
            trans = new ModbusTCPTransaction(con);
            trans.setRequest(rreq);
            System.out.println( "--- Message: Line:46 success --- " );
            // 5r. Execute the READ transaction
            trans.execute();
            rres = (ReadInputRegistersResponse) trans.getResponse();
            System.out.println("Hex Value of register " + "= "
                    + rres.getHexMessage());

            // ~~~~~~~~~~~~~~~~~~~~ The functional Write Request
            // ~~~~~~~~~~~~~~~~~~~~
            // 3w. Prepare the request
            //req = new WriteCoilRequest(coil, true); // Switching ON the "DO 1"
                                                    // (= address 17)

            // 4w. Prepare the transaction
            trans = new ModbusTCPTransaction(con);
            trans.setRequest(req);

            // 5w. Execute the transaction repeat times
            trans.execute();

            // 6. Close the connection
            con.close();

        } catch (Exception ex) {
            System.out.println("Error");
            ex.printStackTrace();
        }
    }
}

最佳答案

Exception in thread "main" java.lang.Error: Unresolved compilation problem: MAX_IP_MESSAGE_LENGTH cannot be resolved or is not a field

表示编译器找不到（恒定）值MAX_IP_MESSAGE_LENGTH。

在net.wimpi.modbus.io.ModbusTCPTransport.prepareStreams（ModbusTCPTransport.java:223）

表示在ModbusTCPTransport.java的第223行MAX_IP_MESSAGE_LENGTH被引用。

问题不在于您的代码，而在于jamod库的编译中。您是否已将jamod的代码复制到您的项目中，或者已将jamod的jar包含到类路径中？如果第一个问题是您的问题，请解决后者（使用maven http://mvnrepository.com/artifact/net.wimpi/jamod/1.2）。