modbus timeout as argument

Author: NikolasK-git

CMakeLists.txt

@@ -4,7 +4,7 @@ cmake_minimum_required(VERSION 3.13.4 FATAL_ERROR)
 # ======================================================================================================================
 
 # project
-project(Modbus_TCP_client_shm LANGUAGES CXX VERSION 1.0.3)
+project(Modbus_TCP_client_shm LANGUAGES CXX VERSION 1.1.0)
 
 # settings
 set(Target "Modbus_TCP_client_shm")    # Executable name (without file extension!)

src/Modbus_TCP_Slave.cpp

@@ -86,5 +86,41 @@ bool Slave::handle_request() {
     return false;
 }
 
+struct timeout_t {
+    uint32_t sec;
+    uint32_t usec;
+};
+
+static inline timeout_t double_to_timeout_t(double timeout) {
+    timeout_t ret{};
+
+    ret.sec = static_cast<uint32_t>(timeout);
+
+    double fractional = timeout - static_cast<double>(ret.sec);
+    ret.usec = static_cast<uint32_t>(fractional * 1000.0 * 1000.0);
+
+    return ret;
+}
+
+void Slave::set_byte_timeout(double timeout) {
+    const auto T = double_to_timeout_t(timeout);
+    auto ret = modbus_set_byte_timeout(modbus, T.sec, T.usec);
+
+    if (ret != 0) {
+        const std::string error_msg = modbus_strerror(errno);
+        throw std::runtime_error("modbus_receive failed: " + error_msg + ' ' + std::to_string(errno));
+    }
+}
+
+void Slave::set_response_timeout(double timeout) {
+    const auto T = double_to_timeout_t(timeout);
+    auto ret = modbus_set_response_timeout(modbus, T.sec, T.usec);
+
+    if (ret != 0) {
+        const std::string error_msg = modbus_strerror(errno);
+        throw std::runtime_error("modbus_receive failed: " + error_msg + ' ' + std::to_string(errno));
+    }
+}
+
 }  // namespace TCP
 }  // namespace Modbus

src/Modbus_TCP_Slave.hpp

@@ -52,6 +52,24 @@ class Slave {
      */
     bool handle_request();
 
+    /*!
+     * \brief set byte timeout
+     *
+     * @details see https://libmodbus.org/docs/v3.1.7/modbus_set_byte_timeout.html
+     *
+     * @param timeout byte timeout in seconds
+     */
+    void set_byte_timeout(double timeout);
+
+    /*!
+     * \brief set byte timeout
+     *
+     * @details see https://libmodbus.org/docs/v3.1.7/modbus_set_response_timeout.html
+     *
+     * @param timeout byte response in seconds
+     */
+    void set_response_timeout(double timeout);
+
     /*! \brief get the modbus socket
      *
      * @return socket of the modbus connection

src/main.cpp

@@ -86,6 +86,19 @@ int main(int argc, char **argv) {
                           "output all incoming and outgoing packets to stdout")
                          ("r,reconnect",
                           "do not terminate if Master disconnects.")
+                         ("byte-timeout",
+                          "timeout interval in seconds between two consecutive bytes of the same message. "
+                           "In most cases it is sufficient to set teh response timeout. "
+                           "Fractional values are possible.",
+                          cxxopts::value<double>())
+                         ("t,response-timeout",
+                          "set the timeout interval in seconds used to wait for a response. "
+                          "When a byte timeout is set, if elapsed time for the first byte of response is longer than "
+                          "the given timeout, the a timeout is detected."
+                          "When byte timeout is disabled, the full confirmation response must be received before "
+                          "expiration of the response timeout."
+                          "Fractional values are possible.",
+                          cxxopts::value<double>())
                          ("h,help",
                           "print usage")
                          ("version",
@@ -174,6 +187,20 @@ int main(int argc, char **argv) {
     }
     socket = slave->get_socket();
 
+    // set timeouts if required
+    try {
+        if (args.count("response-timeout")) {
+            slave->set_response_timeout(args["response-timeout"].as<double>());
+        }
+
+        if (args.count("byte-timeout")) {
+            slave->set_response_timeout(args["byte-timeout"].as<double>());
+        }
+    } catch (const std::runtime_error &e) {
+        std::cerr << e.what() << std::endl;
+        exit(EX_SOFTWARE);
+    }
+
     // connection loop
     do {
         // connect client