ESP32學(xué)習(xí)筆記（8）——TCP客戶端

一、TCP與UDP優(yōu)缺點(diǎn)

1、TCP面向連接（如打電話要先撥號建立連接）;UDP是無連接的，即發(fā)送數(shù)據(jù)之前不需要建立連接。

2、TCP提供可靠的服務(wù)。也就是說，通過TCP連接傳送的數(shù)據(jù)，無差錯，不丟失，不重復(fù)，且按序到達(dá);UDP盡最大努力交付，即不保證可靠交付。
TCP通過校驗(yàn)和，重傳控制，序號標(biāo)識，滑動窗口、確認(rèn)應(yīng)答實(shí)現(xiàn)可靠傳輸。如丟包時的重發(fā)控制，還可以對次序亂掉的分包進(jìn)行順序控制。

3、UDP具有較好的實(shí)時性，工作效率比TCP高，適用于對高速傳輸和實(shí)時性有較高的通信或廣播通信。

4、每一條TCP連接只能是點(diǎn)到點(diǎn)的;UDP支持一對一，一對多，多對一和多對多的交互通信。

5、TCP對系統(tǒng)資源要求較多，UDP對系統(tǒng)資源要求較少。

二、概述

ESP-IDF使用開源 lwIP輕量級的TCP / IP堆棧。ESP-IDF版本lwIP（esp-lwip）與上游項(xiàng)目相比有一些修改和補(bǔ)充。

ESP-IDF支持以下功能 lwIP TCP / IP堆棧功能：

BSD套接字API

BSD套接字API是一個通用的跨平臺TCP / IP套接字API，該API起源于UNIX的Berkeley標(biāo)準(zhǔn)發(fā)行版，但現(xiàn)在已在POSIX規(guī)范的一部分中進(jìn)行了標(biāo)準(zhǔn)化。BSD套接字有時稱為POSIX套接字或Berkeley套接字。

正如ESP-IDF中實(shí)施的那樣，lwIP支持BSD套接字API的所有常用用法。

ESP-IDF 編程指南——ESP-NETIF
ESP-IDF 編程指南——lwIP

三、API說明

以下 BSD Socket 接口位于 lwip/lwip/src/include/lwip/sockets.h。

  • socket()
  • bind()
  • accept()
  • shutdown()
  • getpeername()
  • getsockopt()＆setsockopt()（請參閱套接字選項(xiàng)）
  • close()（通過虛擬文件系統(tǒng)組件）
  • read()，readv()，write()，writev()（經(jīng)由虛擬文件系統(tǒng)部件）
  • recv()，recvmsg()，recvfrom()
  • send()，sendmsg()，sendto()
  • select()（通過虛擬文件系統(tǒng)組件）
  • poll()（注意：在ESP-IDF上，poll()是通過內(nèi)部調(diào)用select來實(shí)現(xiàn)的，因此，select()如果有可用的方法選擇，建議直接使用。）
  • fcntl()（請參閱fcntl）

非標(biāo)準(zhǔn)功能：

  • ioctl()（請參閱ioctls）

四、TCP客戶端

4.1 主要流程


4.1.1 第一步：新建socket

int addr_family = 0;
int ip_protocol = 0;

addr_family = AF_INET;
ip_protocol = IPPROTO_IP;

int sock =  socket(addr_family, SOCK_STREAM, ip_protocol);
if(sock < 0) 
{
    ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
    // 新建失敗后，關(guān)閉新建的socket，等待下次新建
    close(sock);
}

4.1.2 第二步：配置將要連接的服務(wù)器信息（端口和IP）

#define TCP_SERVER_ADRESS    "192.168.61.217"    // 要連接TCP服務(wù)器地址
#define TCP_PORT             3333                // 要連接TCP服務(wù)器端口號

struct sockaddr_in dest_addr;
dest_addr.sin_family = AF_INET;
dest_addr.sin_addr.s_addr = inet_addr(TCP_SERVER_ADRESS);
dest_addr.sin_port = htons(TCP_PORT);

4.1.3 第三步：連接服務(wù)器

int err = connect(sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr);
if(err != 0) 
{
    ESP_LOGE(TAG, "Socket unable to connect: errno %d", errno);
    // 連接失敗后，關(guān)閉之前新建的socket，等待下次新建
    close(sock);
}

4.1.4 第四步：接收數(shù)據(jù)

char rx_buffer[128];

while (1) 
{
    ······
    int len = recv(sock, rx_buffer, sizeof(rx_buffer), 0);
    // Error occurred during receiving
    if (len < 0) 
    {
        ESP_LOGE(TAG, "recv failed: errno %d", errno);
        break;
    }
    // Data received
    else 
    {
        memset(rx_buffer, 0, sizeof(rx_buffer));
        ESP_LOGI(TAG, "Received %d bytes from %s:", len, TCP_SERVER_ADRESS);
        ESP_LOGI(TAG, "%s", rx_buffer);
    }
}

4.1.5 第五步：發(fā)送數(shù)據(jù)

static const char *payload = "Message from ESP32 ";

int err = send(sock, payload, strlen(payload), 0);
if (err < 0) 
{
    ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
}

4.2 配置SSID和密碼連接WIFI創(chuàng)建TCP客戶端


使用 esp-idf\examples\protocols\sockets\tcp_client 中的例程

/* BSD Socket API Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"
#include "addr_from_stdin.h"
#include "lwip/err.h"
#include "lwip/sockets.h"


#if defined(CONFIG_EXAMPLE_IPV4)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV4_ADDR
#elif defined(CONFIG_EXAMPLE_IPV6)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV6_ADDR
#else
#define HOST_IP_ADDR ""
#endif

#define PORT CONFIG_EXAMPLE_PORT

static const char *TAG = "example";
static const char *payload = "Message from ESP32 ";

static void tcp_client_task(void *pvParameters)
{
    char rx_buffer[128];
    char host_ip[] = HOST_IP_ADDR;
    int addr_family = 0;
    int ip_protocol = 0;

    while (1) {
#if defined(CONFIG_EXAMPLE_IPV4)
        struct sockaddr_in dest_addr;
        dest_addr.sin_addr.s_addr = inet_addr(host_ip);
        dest_addr.sin_family = AF_INET;
        dest_addr.sin_port = htons(PORT);
        addr_family = AF_INET;
        ip_protocol = IPPROTO_IP;
#elif defined(CONFIG_EXAMPLE_IPV6)
        struct sockaddr_in6 dest_addr = { 0 };
        inet6_aton(host_ip, &dest_addr.sin6_addr);
        dest_addr.sin6_family = AF_INET6;
        dest_addr.sin6_port = htons(PORT);
        dest_addr.sin6_scope_id = esp_netif_get_netif_impl_index(EXAMPLE_INTERFACE);
        addr_family = AF_INET6;
        ip_protocol = IPPROTO_IPV6;
#elif defined(CONFIG_EXAMPLE_SOCKET_IP_INPUT_STDIN)
        struct sockaddr_in6 dest_addr = { 0 };
        ESP_ERROR_CHECK(get_addr_from_stdin(PORT, SOCK_STREAM, &ip_protocol, &addr_family, &dest_addr));
#endif
        int sock =  socket(addr_family, SOCK_STREAM, ip_protocol);
        if (sock < 0) {
            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
            break;
        }
        ESP_LOGI(TAG, "Socket created, connecting to %s:%d", host_ip, PORT);

        int err = connect(sock, (struct sockaddr *)&dest_addr, sizeof(struct sockaddr_in6));
        if (err != 0) {
            ESP_LOGE(TAG, "Socket unable to connect: errno %d", errno);
            break;
        }
        ESP_LOGI(TAG, "Successfully connected");

        while (1) {
            int err = send(sock, payload, strlen(payload), 0);
            if (err < 0) {
                ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
                break;
            }

            int len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
            // Error occurred during receiving
            if (len < 0) {
                ESP_LOGE(TAG, "recv failed: errno %d", errno);
                break;
            }
            // Data received
            else {
                rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string
                ESP_LOGI(TAG, "Received %d bytes from %s:", len, host_ip);
                ESP_LOGI(TAG, "%s", rx_buffer);
            }

            vTaskDelay(2000 / portTICK_PERIOD_MS);
        }

        if (sock != -1) {
            ESP_LOGE(TAG, "Shutting down socket and restarting...");
            shutdown(sock, 0);
            close(sock);
        }
    }
    vTaskDelete(NULL);
}

void app_main(void)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    ESP_ERROR_CHECK(example_connect());

    xTaskCreate(tcp_client_task, "tcp_client", 4096, NULL, 5, NULL);
}

idf.py menuconfig 配置服務(wù)器IP和端口


配置SSID和密碼



然后 idf.py flash 編譯下載

查看打?。?/p>


4.3 使用SmartConfig連接WIFI創(chuàng)建TCP客戶端


根據(jù) esp-idf\examples\protocols\sockets\tcp_client 中的例程修改

/* BSD Socket API Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <string.h>
#include <sys/param.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/event_groups.h"
#include "esp_system.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_netif.h"
#include "protocol_examples_common.h"
#include "addr_from_stdin.h"
#include "lwip/err.h"
#include "lwip/sockets.h"
#include "esp_smartconfig.h"

#if defined(CONFIG_EXAMPLE_IPV4)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV4_ADDR
#elif defined(CONFIG_EXAMPLE_IPV6)
#define HOST_IP_ADDR CONFIG_EXAMPLE_IPV6_ADDR
#else
#define HOST_IP_ADDR ""
#endif

#define PORT CONFIG_EXAMPLE_PORT

static const char *TAG = "example";
static const char *payload = "Message from ESP32 ";

/* The event group allows multiple bits for each event,
   but we only care about one event - are we connected
   to the AP with an IP? */
static const int CONNECTED_BIT = BIT0;
static const int ESPTOUCH_DONE_BIT = BIT1;

/* FreeRTOS event group to signal when we are connected & ready to make a request */
static EventGroupHandle_t s_wifi_event_group;

static void smartconfig_example_task(void * parm);
static void tcp_client_task(void *pvParameters);

static void event_handler(void* arg, esp_event_base_t event_base, 
                                int32_t event_id, void* event_data)
{
    if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_START) {
        xTaskCreate(smartconfig_example_task, "smartconfig_example_task", 4096, NULL, 3, NULL);
    } else if (event_base == WIFI_EVENT && event_id == WIFI_EVENT_STA_DISCONNECTED) {
        esp_wifi_connect();
        xEventGroupClearBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == IP_EVENT && event_id == IP_EVENT_STA_GOT_IP) {
        xEventGroupSetBits(s_wifi_event_group, CONNECTED_BIT);
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SCAN_DONE) {
        ESP_LOGI(TAG, "Scan done");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_FOUND_CHANNEL) {
        ESP_LOGI(TAG, "Found channel");
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_GOT_SSID_PSWD) {
        ESP_LOGI(TAG, "Got SSID and password");

        smartconfig_event_got_ssid_pswd_t *evt = (smartconfig_event_got_ssid_pswd_t *)event_data;
        wifi_config_t wifi_config;
        uint8_t ssid[33] = { 0 };
        uint8_t password[65] = { 0 };

        bzero(&wifi_config, sizeof(wifi_config_t));
        memcpy(wifi_config.sta.ssid, evt->ssid, sizeof(wifi_config.sta.ssid));
        memcpy(wifi_config.sta.password, evt->password, sizeof(wifi_config.sta.password));
        wifi_config.sta.bssid_set = evt->bssid_set;
        if (wifi_config.sta.bssid_set == true) {
            memcpy(wifi_config.sta.bssid, evt->bssid, sizeof(wifi_config.sta.bssid));
        }

        memcpy(ssid, evt->ssid, sizeof(evt->ssid));
        memcpy(password, evt->password, sizeof(evt->password));
        ESP_LOGI(TAG, "SSID:%s", ssid);
        ESP_LOGI(TAG, "PASSWORD:%s", password);

        ESP_ERROR_CHECK( esp_wifi_disconnect() );
        ESP_ERROR_CHECK( esp_wifi_set_config(ESP_IF_WIFI_STA, &wifi_config) );
        ESP_ERROR_CHECK( esp_wifi_connect() );
    } else if (event_base == SC_EVENT && event_id == SC_EVENT_SEND_ACK_DONE) {
        xEventGroupSetBits(s_wifi_event_group, ESPTOUCH_DONE_BIT);
    }
}

static void initialise_wifi(void)
{
    ESP_ERROR_CHECK(esp_netif_init());
    s_wifi_event_group = xEventGroupCreate();
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_t *sta_netif = esp_netif_create_default_wifi_sta();
    assert(sta_netif);

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_wifi_init(&cfg) );

    ESP_ERROR_CHECK( esp_event_handler_register(WIFI_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(IP_EVENT, IP_EVENT_STA_GOT_IP, &event_handler, NULL) );
    ESP_ERROR_CHECK( esp_event_handler_register(SC_EVENT, ESP_EVENT_ANY_ID, &event_handler, NULL) );

    ESP_ERROR_CHECK( esp_wifi_set_mode(WIFI_MODE_STA) );
    ESP_ERROR_CHECK( esp_wifi_start() );
}

static void smartconfig_example_task(void * parm)
{
    EventBits_t uxBits;
    ESP_ERROR_CHECK( esp_smartconfig_set_type(SC_TYPE_ESPTOUCH_AIRKISS) );
    smartconfig_start_config_t cfg = SMARTCONFIG_START_CONFIG_DEFAULT();
    ESP_ERROR_CHECK( esp_smartconfig_start(&cfg) );
    while (1) {
        uxBits = xEventGroupWaitBits(s_wifi_event_group, CONNECTED_BIT | ESPTOUCH_DONE_BIT, true, false, portMAX_DELAY); 
        if(uxBits & CONNECTED_BIT) {
            ESP_LOGI(TAG, "WiFi Connected to ap");
        }
        if(uxBits & ESPTOUCH_DONE_BIT) {
            ESP_LOGI(TAG, "smartconfig over");
            xTaskCreate(tcp_client_task, "tcp_client", 4096, NULL, 5, NULL);
            esp_smartconfig_stop();
            vTaskDelete(NULL);
        }
    }
}

static void tcp_client_task(void *pvParameters)
{
    char rx_buffer[128];
    char host_ip[] = HOST_IP_ADDR;
    int addr_family = 0;
    int ip_protocol = 0;

    while (1) {
#if defined(CONFIG_EXAMPLE_IPV4)
        struct sockaddr_in dest_addr;
        dest_addr.sin_addr.s_addr = inet_addr(host_ip);
        dest_addr.sin_family = AF_INET;
        dest_addr.sin_port = htons(PORT);
        addr_family = AF_INET;
        ip_protocol = IPPROTO_IP;
#elif defined(CONFIG_EXAMPLE_IPV6)
        struct sockaddr_in6 dest_addr = { 0 };
        inet6_aton(host_ip, &dest_addr.sin6_addr);
        dest_addr.sin6_family = AF_INET6;
        dest_addr.sin6_port = htons(PORT);
        dest_addr.sin6_scope_id = esp_netif_get_netif_impl_index(EXAMPLE_INTERFACE);
        addr_family = AF_INET6;
        ip_protocol = IPPROTO_IPV6;
#elif defined(CONFIG_EXAMPLE_SOCKET_IP_INPUT_STDIN)
        struct sockaddr_in6 dest_addr = { 0 };
        ESP_ERROR_CHECK(get_addr_from_stdin(PORT, SOCK_STREAM, &ip_protocol, &addr_family, &dest_addr));
#endif
        int sock =  socket(addr_family, SOCK_STREAM, ip_protocol);
        if (sock < 0) {
            ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
            break;
        }
        ESP_LOGI(TAG, "Socket created, connecting to %s:%d", host_ip, PORT);

        int err = connect(sock, (struct sockaddr *)&dest_addr, sizeof(struct sockaddr_in6));
        if (err != 0) {
            ESP_LOGE(TAG, "Socket unable to connect: errno %d", errno);
            break;
        }
        ESP_LOGI(TAG, "Successfully connected");

        while (1) {
            int err = send(sock, payload, strlen(payload), 0);
            if (err < 0) {
                ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
                break;
            }

            int len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
            // Error occurred during receiving
            if (len < 0) {
                ESP_LOGE(TAG, "recv failed: errno %d", errno);
                break;
            }
            // Data received
            else {
                rx_buffer[len] = 0; // Null-terminate whatever we received and treat like a string
                ESP_LOGI(TAG, "Received %d bytes from %s:", len, host_ip);
                ESP_LOGI(TAG, "%s", rx_buffer);
            }

            vTaskDelay(2000 / portTICK_PERIOD_MS);
        }

        if (sock != -1) {
            ESP_LOGE(TAG, "Shutting down socket and restarting...");
            shutdown(sock, 0);
            close(sock);
        }
    }
    vTaskDelete(NULL);
}

void app_main(void)
{
    ESP_ERROR_CHECK(nvs_flash_init());
    initialise_wifi();
    // ESP_ERROR_CHECK(esp_netif_init());
    // ESP_ERROR_CHECK(esp_event_loop_create_default());

    /* This helper function configures Wi-Fi or Ethernet, as selected in menuconfig.
     * Read "Establishing Wi-Fi or Ethernet Connection" section in
     * examples/protocols/README.md for more information about this function.
     */
    // ESP_ERROR_CHECK(example_connect());

    // xTaskCreate(tcp_client_task, "tcp_client", 4096, NULL, 5, NULL);
}

idf.py menuconfig 配置服務(wù)器IP和端口


然后 idf.py flash 編譯下載

查看打印：


? 由 Leung 寫于 2021 年 4 月 26 日

? 參考：第十六章 ESP32的TCP連接
　　　　樂鑫Esp32學(xué)習(xí)之旅⑨ esp32上實(shí)現(xiàn)本地 TCP 客戶端和服務(wù)端角色，可斷線重連原路返回數(shù)據(jù)
　　　　ESP32 開發(fā)筆記(三）源碼示例 21_WIFI_STA_TCP_Client 在站模式STA下實(shí)現(xiàn)TCP客戶端
　　　　ESP32TCP-CLIENT 通信
　　　　ESP32開發(fā)之路（7）---ESP32作為TCP客戶端連接到局域網(wǎng)的PC機(jī)

?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時請結(jié)合常識與多方信息審慎甄別。
平臺聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點(diǎn)，簡書系信息發(fā)布平臺，僅提供信息存儲服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容