esp32 tcp连接中断 esp32 tcp速度

一、TCP与UDP优缺点

1、TCP面向连接（如打电话要先拨号建立连接）;UDP是无连接的，即发送数据之前不需要建立连接。

2、TCP提供可靠的服务。也就是说，通过TCP连接传送的数据，无差错，不丢失，不重复，且按序到达;UDP尽最大努力交付，即不保证可靠交付。
TCP通过校验和，重传控制，序号标识，滑动窗口、确认应答实现可靠传输。如丢包时的重发控制，还可以对次序乱掉的分包进行顺序控制。

3、UDP具有较好的实时性，工作效率比TCP高，适用于对高速传输和实时性有较高的通信或广播通信。

4、每一条TCP连接只能是点到点的;UDP支持一对一，一对多，多对一和多对多的交互通信。

5、TCP对系统资源要求较多，UDP对系统资源要求较少。

二、概述

ESP-IDF使用开源 lwIP轻量级的TCP / IP堆栈。ESP-IDF版本lwIP（esp-lwip）与上游项目相比有一些修改和补充。

ESP-IDF支持以下功能 lwIP TCP / IP堆栈功能：

• BSD套接字API
• Netconn API已启用，但ESP-IDF应用程序未正式支持

BSD套接字API

BSD套接字API是一个通用的跨平台TCP / IP套接字API，该API起源于UNIX的Berkeley标准发行版，但现在已在POSIX规范的一部分中进行了标准化。BSD套接字有时称为POSIX套接字或Berkeley套接字。

正如ESP-IDF中实施的那样，lwIP支持BSD套接字API的所有常用用法。

ESP-IDF 编程指南——ESP-NETIFESP-IDF 编程指南——lwIP

三、API说明

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

• socket()
• bind()
• accept()
• shutdown()
• getpeername()
• getsockopt()＆setsockopt()（请参阅套接字选项）
• close()（通过虚拟文件系统组件）
• read()，readv()，write()，writev()（经由虚拟文件系统部件）
• recv()，recvmsg()，recvfrom()
• send()，sendmsg()，sendto()
• select()（通过虚拟文件系统组件）
• poll()（注意：在ESP-IDF上，poll()是通过内部调用select来实现的，因此，select()如果有可用的方法选择，建议直接使用。）
• fcntl()（请参阅fcntl）

非标准功能：

• ioctl()（请参阅ioctls）

四、TCP客户端

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);
    // 新建失败后，关闭新建的socket，等待下次新建
    close(sock);
}

4.1.2 第二步：配置将要连接的服务器信息（端口和IP）

#define TCP_SERVER_ADRESS    "192.168.61.217"    // 要连接TCP服务器地址
#define TCP_PORT             3333                // 要连接TCP服务器端口号

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：连接服务器

int err = connect(sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr);
if(err != 0) 
{
    ESP_LOGE(TAG, "Socket unable to connect: errno %d", errno);
    // 连接失败后，关闭之前新建的socket，等待下次新建
    close(sock);
}

4.1.4 第四步：接收数据

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：发送数据

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和密码连接WIFI创建TCP客户端

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 配置服务器IP和端口

配置SSID和密码

然后 idf.py flash 编译下载

查看打印：

4.3 使用SmartConfig连接WIFI创建TCP客户端

根据 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 配置服务器IP和端口

然后 idf.py flash 编译下载

查看打印：

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作者： Leung