一个基于 ESP-IDF 的 RPC over UDP 示例

创建了一个基于 ESP-IDF 的 RPC over UDP 示例，包括服务端与客户端的完整代码。您可以查看并根据需求调整方法名、参数解析和网络配置等

/*

• ESP32 RPC over UDP Example (Detailed Version)
• Description:
• This example demonstrates a simple Remote Procedure Call (RPC) mechanism
• over UDP. An ESP32 device acts as both server and client in separate RTOS tasks.
• • The server listens on a UDP port and handles incoming requests of the form:

    <method>:<arg1>,<arg2>\n

  Supported methods:

    add - return sum of two integers

    sub - return difference between two integers (arg1 - arg2)

• • The client periodically sends RPC commands to the server and logs the responses.
• Key Components:
• • FreeRTOS tasks: udp_server_task, udp_client_task
• • BSD sockets: socket(), bind(), recvfrom(), sendto()
• • Simple parsing via sscanf() and strcmp()
• Configuration:
• • SERVER_PORT: UDP port on which server listens
• • CLIENT_PORT: UDP port bound by client to receive responses
• • CONFIG_EXAMPLE_SERVER_IP: set to server IP in menuconfig
• ESP-IDF Requirements:
• • esp_netif (network interface)
• • Wi-Fi or Ethernet connectivity established via example_connect()
• • NVS flash initialization for Wi-Fi credentials
    */

#include <string.h>

#include <stdio.h>

#include <errno.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <freertos/FreeRTOS.h>

#include <freertos/task.h>

#include <esp_system.h>

#include <esp_log.h>

#include <nvs_flash.h>

#include <esp_netif.h>

#include <esp_event.h>

#include <esp_wifi.h>

#include <protocol_examples_common.h> // For example_connect()

// UDP port definitions

#define SERVER_PORT 3333 // Port on which the RPC server listens

#define CLIENT_PORT 4444 // Local port for RPC client to receive responses

#define BUF_SIZE 128 // Maximum buffer size for UDP packets

static const char *TAG = "rpc_udp"; // Logging tag

/**

• @brief Simple RPC handler function.
• Parses the incoming request string and executes the requested method.
• @param req The null-terminated request string, e.g. "add:2,3".
• @param resp Buffer to write the null-terminated response.
• @param resp_max_len Maximum length of the response buffer.
• @return Number of bytes written into resp (excluding null terminator),

      or negative on error.

/
static int rpc_handler(const char req, char* resp, size_t resp_max_len)

{

char method[16]; // Buffer for method name ("add" or "sub")

int arg1 = 0;

int arg2 = 0;

// Use sscanf to extract method and two integer arguments.
// Format: <method>:<arg1>,<arg2>
int parsed = sscanf(req, "%15[^:]:%d,%d", method, &arg1, &arg2);
if (parsed != 3) {
    // Parsing failed: invalid format
    return snprintf(resp, resp_max_len, "error: invalid format");
}

// Dispatch based on method name
if (strcmp(method, "add") == 0) {
    int result = arg1 + arg2;
    return snprintf(resp, resp_max_len, "%d", result);
} else if (strcmp(method, "sub") == 0) {
    int result = arg1 - arg2;
    return snprintf(resp, resp_max_len, "%d", result);
}

// Unknown method
return snprintf(resp, resp_max_len, "error: unknown method");

}

/**

• @brief UDP RPC server task.

• Creates a UDP socket, binds to SERVER_PORT, and waits for incoming requests.

• For each request, calls rpc_handler() and sends the response back to the client.
  /
  static void udp_server_task(void arg)

  {

  char rx_buffer[BUF_SIZE]; // Buffer for incoming request

  char addr_str[INET_ADDRSTRLEN]; // Human-readable client IP

  struct sockaddr_in server_addr, client_addr;

  socklen_t addr_len = sizeof(client_addr);

  // Create UDP socket

  int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

  if (sock < 0) {

  ESP_LOGE(TAG, "Failed to create socket: errno %d", errno);

  vTaskDelete(NULL);

  return;

  }

  // Prepare server address struct

  server_addr.sin_family = AF_INET;

  server_addr.sin_addr.s_addr = htonl(INADDR_ANY); // Listen on all interfaces

  server_addr.sin_port = htons(SERVER_PORT);

  // Bind socket to the specified port

  if (bind(sock, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0) {

  ESP_LOGE(TAG, "Socket bind failed: errno %d", errno);

  close(sock);

  vTaskDelete(NULL);

  return;

  }

  ESP_LOGI(TAG, "UDP server listening on port %d", SERVER_PORT);

  while (1) {

  // Receive a UDP packet

  int len = recvfrom(sock, rx_buffer, BUF_SIZE - 1, 0,

  (struct sockaddr*)&client_addr, &addr_len);

  if (len < 0) {

  ESP_LOGE(TAG, "recvfrom error: errno %d", errno);

  break;

  }

   // Null-terminate and log request
   rx_buffer[len] = '\0';
   inet_ntoa_r(client_addr.sin_addr, addr_str, sizeof(addr_str));
   ESP_LOGI(TAG, "Received %d bytes from %s:%d", len,
            addr_str, ntohs(client_addr.sin_port));
   ESP_LOGI(TAG, "Request: %s", rx_buffer);
  
   // Process the RPC command
   char response[BUF_SIZE];
   int resp_len = rpc_handler(rx_buffer, response, sizeof(response));
  
   // Send response back to the client
   int err = sendto(sock, response, resp_len, 0,
                    (struct sockaddr*)&client_addr, addr_len);
   if (err < 0) {
       ESP_LOGE(TAG, "sendto error: errno %d", errno);
       break;
   }

  }

  // Clean up socket and task

  close(sock);

  vTaskDelete(NULL);

  }

/**

• @brief UDP RPC client task (example usage).

• Sends predefined RPC commands to the server and logs the responses.
  /
  static void udp_client_task(void arg)

  {

  char rx_buffer[BUF_SIZE]; // Buffer for incoming response

  struct sockaddr_in dest_addr;

  dest_addr.sin_family = AF_INET;

  dest_addr.sin_addr.s_addr = inet_addr(CONFIG_EXAMPLE_SERVER_IP);

  dest_addr.sin_port = htons(SERVER_PORT);

  // Create UDP socket

  int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);

  if (sock < 0) {

  ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);

  vTaskDelete(NULL);

  return;

  }

  // Bind client socket to receive responses on CLIENT_PORT

  struct sockaddr_in client_addr = {

  .sin_family = AF_INET,

  .sin_addr.s_addr = htonl(INADDR_ANY),

  .sin_port = htons(CLIENT_PORT)

  };

  if (bind(sock, (struct sockaddr*)&client_addr, sizeof(client_addr)) < 0) {

  ESP_LOGE(TAG, "Client bind failed: errno %d", errno);

  close(sock);

  vTaskDelete(NULL);

  return;

  }

  // Example RPC commands

  const char* rpc_cmds[] = { "add:5,3", "sub:10,4" };

  size_t cmd_count = sizeof(rpc_cmds) / sizeof(rpc_cmds[0]);

  for (size_t i = 0; i < cmd_count; i++) {

  // Send RPC command

  ESP_LOGI(TAG, "Sending RPC command: %s", rpc_cmds[i]);

  sendto(sock, rpc_cmds[i], strlen(rpc_cmds[i]), 0,

  (struct sockaddr*)&dest_addr, sizeof(dest_addr));

   // Wait for response (blocking)
   int len = recvfrom(sock, rx_buffer, BUF_SIZE - 1, 0, NULL, NULL);
   if (len < 0) {
       ESP_LOGE(TAG, "recvfrom failed: errno %d", errno);
       break;
   }
   rx_buffer[len] = '\0';  // Null-terminate
   ESP_LOGI(TAG, "RPC response: %s", rx_buffer);
  
   // Delay before next command
   vTaskDelay(pdMS_TO_TICKS(2000));

  }

  // Clean up

  close(sock);

  vTaskDelete(NULL);

  }

/**

• @brief Main application entry point.

• Initializes NVS, network interfaces, connects to Wi-Fi/Ethernet,

• and launches the UDP server and client tasks.

  */

  void app_main(void)

  {

  // 1. Initialize NVS for Wi-Fi credentials storage

  esp_err_t ret = nvs_flash_init();

  if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {

  ESP_ERROR_CHECK(nvs_flash_erase());

  ret = nvs_flash_init();

  }

  ESP_ERROR_CHECK(ret);

  // 2. Initialize TCP/IP network interface

  ESP_ERROR_CHECK(esp_netif_init());

  // 3. Create default event loop

  ESP_ERROR_CHECK(esp_event_loop_create_default());

  // 4. Connect to configured Wi-Fi or Ethernet network

  // This call blocks until an IP address is obtained.

  example_connect();

  // 5. Start the RPC server and client tasks

  xTaskCreate(udp_server_task, "udp_server_task", 4096, NULL, 5, NULL);

  xTaskCreate(udp_client_task, "udp_client_task", 4096, NULL, 5, NULL);

  }