一陵珍、TCP與UDP優(yōu)缺點
1寝杖、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互纯。
2瑟幕、TCP提供可靠的服務。也就是說留潦,通過TCP連接傳送的數(shù)據(jù)只盹,無差錯,不丟失兔院,不重復殖卑,且按序到達;UDP盡最大努力交付,即不保證可靠交付坊萝。
TCP通過校驗和孵稽,重傳控制,序號標識十偶,滑動窗口菩鲜、確認應答實現(xiàn)可靠傳輸。如丟包時的重發(fā)控制扯键,還可以對次序亂掉的分包進行順序控制睦袖。3、UDP具有較好的實時性荣刑,工作效率比TCP高馅笙,適用于對高速傳輸和實時性有較高的通信或廣播通信。
4厉亏、每一條TCP連接只能是點到點的;UDP支持一對一董习,一對多,多對一和多對多的交互通信爱只。
5皿淋、TCP對系統(tǒng)資源要求較多,UDP對系統(tǒng)資源要求較少恬试。
二窝趣、概述
ESP-IDF使用開源 lwIP輕量級的TCP / IP堆棧。ESP-IDF版本lwIP(esp-lwip)與上游項目相比有一些修改和補充训柴。
ESP-IDF支持以下功能 lwIP TCP / IP堆棧功能:
Netconn API已啟用哑舒,但ESP-IDF應用程序未正式支持
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標準發(fā)行版幻馁,但現(xiàn)在已在POSIX規(guī)范的一部分中進行了標準化洗鸵。BSD套接字有時稱為POSIX套接字或Berkeley套接字越锈。
正如ESP-IDF中實施的那樣,lwIP支持BSD套接字API的所有常用用法膘滨。
ESP-IDF 編程指南——ESP-NETIF
ESP-IDF 編程指南——lwIP
三甘凭、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) -
close()
(通過虛擬文件系統(tǒng)組件) -
read()
火邓,readv()
丹弱,write()
,writev()
(經(jīng)由虛擬文件系統(tǒng)部件) -
recv()
贡翘,recvmsg()
蹈矮,recvfrom()
-
send()
,sendmsg()
鸣驱,sendto()
-
select()
(通過虛擬文件系統(tǒng)組件) -
poll()
(注意:在ESP-IDF上泛鸟,poll()
是通過內(nèi)部調(diào)用select來實現(xiàn)的,因此踊东,select()
如果有可用的方法選擇北滥,建議直接使用。) -
fcntl()
(請參閱fcntl)
非標準功能:
-
ioctl()
(請參閱ioctls)
四闸翅、TCP服務端
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 listen_sock = socket(addr_family, SOCK_STREAM, ip_protocol);
if(listen_sock < 0)
{
ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
}
4.1.2 第二步:配置服務器信息
#define TCP_PORT 3333 // TCP服務器端口號
struct sockaddr_in dest_addr;
dest_addr.sin_family = AF_INET;
dest_addr.sin_addr.s_addr = htonl(INADDR_ANY);
dest_addr.sin_port = htons(TCP_PORT);
4.1.3 第三步:綁定地址
int err = bind(listen_sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
if(err != 0)
{
ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
ESP_LOGE(TAG, "IPPROTO: %d", addr_family);
close(listen_sock);
}
ESP_LOGI(TAG, "Socket bound, port %d", PORT);
4.1.4 第四步:開始監(jiān)聽
err = listen(listen_sock, 1); // 這里為啥是1再芋,網(wǎng)上大多數(shù)是5
if(err != 0)
{
ESP_LOGE(TAG, "Error occurred during listen: errno %d", errno);
close(listen_sock);
}
4.1.5 第五步:等待客戶端連接
while(1)
{
struct sockaddr_in6 source_addr; // Large enough for both IPv4 or IPv6
uint addr_len = sizeof(source_addr);
int connect_sock = accept(listen_sock, (struct sockaddr *)&source_addr, &addr_len);
if(connect_sock < 0)
{
ESP_LOGE(TAG, "Unable to accept connection: errno %d", errno);
close(listen_sock);
}
}
4.1.6 第六步:接收數(shù)據(jù)
int len;
char rx_buffer[128];
while(1)
{
memset(rx_buffer, 0, sizeof(rx_buffer)); // 清空緩存
len = recv(connect_sock, rx_buffer, sizeof(rx_buffer), 0); // 讀取接收數(shù)據(jù)
if(len < 0)
{
ESP_LOGE(TAG, "Error occurred during receiving: errno %d", errno);
}
else if (len == 0)
{
ESP_LOGW(TAG, "Connection closed");
}
else
{
ESP_LOGI(TAG, "Received %d bytes: %s", len, rx_buffer);
}
}
4.1.7 第七步:發(fā)送數(shù)據(jù)
send(connect_socket, rx_buffer, sizeof(rx_buffer, 0);
4.2 配置SSID和密碼連接WIFI創(chuàng)建TCP服務端
TCP Server類似
使用 esp-idf\examples\protocols\sockets\tcp_server 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 "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 "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include <lwip/netdb.h>
#define PORT CONFIG_EXAMPLE_PORT
static const char *TAG = "example";
static void do_retransmit(const int sock)
{
int len;
char rx_buffer[128];
do {
len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
if (len < 0) {
ESP_LOGE(TAG, "Error occurred during receiving: errno %d", errno);
} else if (len == 0) {
ESP_LOGW(TAG, "Connection closed");
} else {
rx_buffer[len] = 0; // Null-terminate whatever is received and treat it like a string
ESP_LOGI(TAG, "Received %d bytes: %s", len, rx_buffer);
// send() can return less bytes than supplied length.
// Walk-around for robust implementation.
int to_write = len;
while (to_write > 0) {
int written = send(sock, rx_buffer + (len - to_write), to_write, 0);
if (written < 0) {
ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
}
to_write -= written;
}
}
} while (len > 0);
}
static void tcp_server_task(void *pvParameters)
{
char addr_str[128];
int addr_family = (int)pvParameters;
int ip_protocol = 0;
struct sockaddr_in6 dest_addr;
if (addr_family == AF_INET) {
struct sockaddr_in *dest_addr_ip4 = (struct sockaddr_in *)&dest_addr;
dest_addr_ip4->sin_addr.s_addr = htonl(INADDR_ANY);
dest_addr_ip4->sin_family = AF_INET;
dest_addr_ip4->sin_port = htons(PORT);
ip_protocol = IPPROTO_IP;
} else if (addr_family == AF_INET6) {
bzero(&dest_addr.sin6_addr.un, sizeof(dest_addr.sin6_addr.un));
dest_addr.sin6_family = AF_INET6;
dest_addr.sin6_port = htons(PORT);
ip_protocol = IPPROTO_IPV6;
}
int listen_sock = socket(addr_family, SOCK_STREAM, ip_protocol);
if (listen_sock < 0) {
ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
vTaskDelete(NULL);
return;
}
#if defined(CONFIG_EXAMPLE_IPV4) && defined(CONFIG_EXAMPLE_IPV6)
// Note that by default IPV6 binds to both protocols, it is must be disabled
// if both protocols used at the same time (used in CI)
int opt = 1;
setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt));
#endif
ESP_LOGI(TAG, "Socket created");
int err = bind(listen_sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
if (err != 0) {
ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
ESP_LOGE(TAG, "IPPROTO: %d", addr_family);
goto CLEAN_UP;
}
ESP_LOGI(TAG, "Socket bound, port %d", PORT);
err = listen(listen_sock, 1);
if (err != 0) {
ESP_LOGE(TAG, "Error occurred during listen: errno %d", errno);
goto CLEAN_UP;
}
while (1) {
ESP_LOGI(TAG, "Socket listening");
struct sockaddr_in6 source_addr; // Large enough for both IPv4 or IPv6
uint addr_len = sizeof(source_addr);
int sock = accept(listen_sock, (struct sockaddr *)&source_addr, &addr_len);
if (sock < 0) {
ESP_LOGE(TAG, "Unable to accept connection: errno %d", errno);
break;
}
// Convert ip address to string
if (source_addr.sin6_family == PF_INET) {
inet_ntoa_r(((struct sockaddr_in *)&source_addr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);
} else if (source_addr.sin6_family == PF_INET6) {
inet6_ntoa_r(source_addr.sin6_addr, addr_str, sizeof(addr_str) - 1);
}
ESP_LOGI(TAG, "Socket accepted ip address: %s", addr_str);
do_retransmit(sock);
shutdown(sock, 0);
close(sock);
}
CLEAN_UP:
close(listen_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());
#ifdef CONFIG_EXAMPLE_IPV4
xTaskCreate(tcp_server_task, "tcp_server", 4096, (void*)AF_INET, 5, NULL);
#endif
#ifdef CONFIG_EXAMPLE_IPV6
xTaskCreate(tcp_server_task, "tcp_server", 4096, (void*)AF_INET6, 5, NULL);
#endif
}
idf.py menuconfig
配置服務器端口
配置SSID和密碼
然后 idf.py flash
編譯下載
查看打印:
連接上WIFI后查看獲取到的IP地址(如192.168.61.107)
打開TCP客戶端坚冀,輸入服務端IP和端口济赎,選擇連接,發(fā)送數(shù)據(jù)
4.3 作為AP創(chuàng)建TCP服務端
根據(jù) esp-idf\examples\protocols\sockets\tcp_server 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 "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 "lwip/err.h"
#include "lwip/sockets.h"
#include "lwip/sys.h"
#include <lwip/netdb.h>
#define PORT CONFIG_EXAMPLE_PORT
#define EXAMPLE_ESP_WIFI_SSID "ESP32_TEST"
#define EXAMPLE_ESP_WIFI_PASS "12345678"
#define EXAMPLE_ESP_WIFI_CHANNEL 1
#define EXAMPLE_MAX_STA_CONN 4
static const char *TAG = "example";
static void wifi_event_handler(void* arg, esp_event_base_t event_base,
int32_t event_id, void* event_data)
{
if (event_id == WIFI_EVENT_AP_STACONNECTED) {
wifi_event_ap_staconnected_t* event = (wifi_event_ap_staconnected_t*) event_data;
ESP_LOGI(TAG, "station "MACSTR" join, AID=%d",
MAC2STR(event->mac), event->aid);
} else if (event_id == WIFI_EVENT_AP_STADISCONNECTED) {
wifi_event_ap_stadisconnected_t* event = (wifi_event_ap_stadisconnected_t*) event_data;
ESP_LOGI(TAG, "station "MACSTR" leave, AID=%d",
MAC2STR(event->mac), event->aid);
}
}
void wifi_init_softap(void)
{
ESP_ERROR_CHECK(esp_netif_init());
ESP_ERROR_CHECK(esp_event_loop_create_default());
esp_netif_create_default_wifi_ap();
wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
ESP_ERROR_CHECK(esp_wifi_init(&cfg));
ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT,
ESP_EVENT_ANY_ID,
&wifi_event_handler,
NULL,
NULL));
wifi_config_t wifi_config = {
.ap = {
.ssid = EXAMPLE_ESP_WIFI_SSID,
.ssid_len = strlen(EXAMPLE_ESP_WIFI_SSID),
.channel = EXAMPLE_ESP_WIFI_CHANNEL,
.password = EXAMPLE_ESP_WIFI_PASS,
.max_connection = EXAMPLE_MAX_STA_CONN,
.authmode = WIFI_AUTH_WPA_WPA2_PSK
},
};
if (strlen(EXAMPLE_ESP_WIFI_PASS) == 0) {
wifi_config.ap.authmode = WIFI_AUTH_OPEN;
}
ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_AP));
ESP_ERROR_CHECK(esp_wifi_set_config(ESP_IF_WIFI_AP, &wifi_config));
ESP_ERROR_CHECK(esp_wifi_start());
ESP_LOGI(TAG, "wifi_init_softap finished. SSID:%s password:%s channel:%d",
EXAMPLE_ESP_WIFI_SSID, EXAMPLE_ESP_WIFI_PASS, EXAMPLE_ESP_WIFI_CHANNEL);
}
static void do_retransmit(const int sock)
{
int len;
char rx_buffer[128];
do {
len = recv(sock, rx_buffer, sizeof(rx_buffer) - 1, 0);
if (len < 0) {
ESP_LOGE(TAG, "Error occurred during receiving: errno %d", errno);
} else if (len == 0) {
ESP_LOGW(TAG, "Connection closed");
} else {
rx_buffer[len] = 0; // Null-terminate whatever is received and treat it like a string
ESP_LOGI(TAG, "Received %d bytes: %s", len, rx_buffer);
// send() can return less bytes than supplied length.
// Walk-around for robust implementation.
int to_write = len;
while (to_write > 0) {
int written = send(sock, rx_buffer + (len - to_write), to_write, 0);
if (written < 0) {
ESP_LOGE(TAG, "Error occurred during sending: errno %d", errno);
}
to_write -= written;
}
}
} while (len > 0);
}
static void tcp_server_task(void *pvParameters)
{
char addr_str[128];
int addr_family = (int)pvParameters;
int ip_protocol = 0;
struct sockaddr_in6 dest_addr;
if (addr_family == AF_INET) {
struct sockaddr_in *dest_addr_ip4 = (struct sockaddr_in *)&dest_addr;
dest_addr_ip4->sin_addr.s_addr = htonl(INADDR_ANY);
dest_addr_ip4->sin_family = AF_INET;
dest_addr_ip4->sin_port = htons(PORT);
ip_protocol = IPPROTO_IP;
} else if (addr_family == AF_INET6) {
bzero(&dest_addr.sin6_addr.un, sizeof(dest_addr.sin6_addr.un));
dest_addr.sin6_family = AF_INET6;
dest_addr.sin6_port = htons(PORT);
ip_protocol = IPPROTO_IPV6;
}
int listen_sock = socket(addr_family, SOCK_STREAM, ip_protocol);
if (listen_sock < 0) {
ESP_LOGE(TAG, "Unable to create socket: errno %d", errno);
vTaskDelete(NULL);
return;
}
#if defined(CONFIG_EXAMPLE_IPV4) && defined(CONFIG_EXAMPLE_IPV6)
// Note that by default IPV6 binds to both protocols, it is must be disabled
// if both protocols used at the same time (used in CI)
int opt = 1;
setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
setsockopt(listen_sock, IPPROTO_IPV6, IPV6_V6ONLY, &opt, sizeof(opt));
#endif
ESP_LOGI(TAG, "Socket created");
int err = bind(listen_sock, (struct sockaddr *)&dest_addr, sizeof(dest_addr));
if (err != 0) {
ESP_LOGE(TAG, "Socket unable to bind: errno %d", errno);
ESP_LOGE(TAG, "IPPROTO: %d", addr_family);
goto CLEAN_UP;
}
ESP_LOGI(TAG, "Socket bound, port %d", PORT);
err = listen(listen_sock, 1);
if (err != 0) {
ESP_LOGE(TAG, "Error occurred during listen: errno %d", errno);
goto CLEAN_UP;
}
while (1) {
ESP_LOGI(TAG, "Socket listening");
struct sockaddr_in6 source_addr; // Large enough for both IPv4 or IPv6
uint addr_len = sizeof(source_addr);
int sock = accept(listen_sock, (struct sockaddr *)&source_addr, &addr_len);
if (sock < 0) {
ESP_LOGE(TAG, "Unable to accept connection: errno %d", errno);
break;
}
// Convert ip address to string
if (source_addr.sin6_family == PF_INET) {
inet_ntoa_r(((struct sockaddr_in *)&source_addr)->sin_addr.s_addr, addr_str, sizeof(addr_str) - 1);
} else if (source_addr.sin6_family == PF_INET6) {
inet6_ntoa_r(source_addr.sin6_addr, addr_str, sizeof(addr_str) - 1);
}
ESP_LOGI(TAG, "Socket accepted ip address: %s", addr_str);
do_retransmit(sock);
shutdown(sock, 0);
close(sock);
}
CLEAN_UP:
close(listen_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());
wifi_init_softap();
#ifdef CONFIG_EXAMPLE_IPV4
xTaskCreate(tcp_server_task, "tcp_server", 4096, (void*)AF_INET, 5, NULL);
#endif
#ifdef CONFIG_EXAMPLE_IPV6
xTaskCreate(tcp_server_task, "tcp_server", 4096, (void*)AF_INET6, 5, NULL);
#endif
}
idf.py menuconfig
配置服務器端口
然后 idf.py flash
編譯下載
查看打蛹悄场:
IP默認是
192.168.4.1
這個是樂鑫在出廠時候?qū)懰赖?p>
打開TCP客戶端司训,輸入服務端IP和端口,選擇連接液南,發(fā)送數(shù)據(jù)
? 由 Leung 寫于 2021 年 4 月 28 日
? 參考:樂鑫Esp32學習之旅⑨ esp32上實現(xiàn)本地 TCP 客戶端和服務端角色壳猜,可斷線重連原路返回數(shù)據(jù)
ESP32 開發(fā)筆記(三)源碼示例 20_WIFI_STA_TCP_Server 在站模式STA下實現(xiàn)TCP服務端
ESP32 開發(fā)筆記(三)源碼示例 16_WIFI_AP_TCP_Server 在AP模式下實現(xiàn)TCP服務端