ESP32 WebsocketsClient连接wss协议的服务器

前言#

硬件：ESP32-S3 开发板
Websocket库：gilmaimon/ArduinoWebsockets@^0.5.4
平台：arduino/PlatformIO

在准备讯飞的大模型前期测试，其api协议从ws替换为了wss后，需要对部分功能进行修改。

在使用官方的python测试案例实现后，移植到arduino上却始终无法连接成功，在逐步测试后最终将问题定位到库上：Arduino ESP32做Websocket client 连接WSS协议的服务器。

ESP32 没有对 client.setInsecure(); 做出响应，即在没有证书时程序无法正常进行，需要修改库的内容。

下面是大致的测试代码：

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#include <Arduino.h>
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#include <WiFi.h>
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#include <ArduinoWebsockets.h>
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using namespace websockets;
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WebsocketsClient client;
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const char* websockets_connection_string = "wss://xxxxxxxxxxxxxx";
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void setup() {
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    led_status_service.init();
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    Serial.begin(115200);
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    while (!Serial)
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    {
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      /* code */
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    }
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    // 连接WiFi
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    WiFi.begin(STA_SSID, STA_PASSWORD);
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    Serial.println("正在连接到WiFI...");
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    while (WiFi.status() != WL_CONNECTED) {
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        delay(600);
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        Serial.print("-");
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    }
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    Serial.println("WiFi 已连接");
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    Serial.println("IP 地址: ");
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    Serial.println(WiFi.localIP());
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    delay(1000);
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    // Before connecting, set the ssl fingerprint of the server
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    client.setInsecure();
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    // client.setCertificate();
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    // client.setCACert();
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    // client.setPrivateKey();
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    // Connect to server
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    if (client.connect(websockets_connection_string)) {
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        Serial.println("yes");
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    } else {
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        Serial.println("no");
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    }
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    // Send a ping
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    client.ping();
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}
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void loop() {
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    client.poll();
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    delay(1); // 避免空循环过快
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}

修改方法#

点击 client.connect 进入 .pio\libdeps\esp32-s3-devkitm-1\ArduinoWebsockets\src\websockets_client.cpp。

找到下面这段关于 wss 协议的连接方法：

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#ifndef _WS_CONFIG_NO_SSL
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    else if(doestStartsWith(url, "wss://")) {
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        defaultPort = 443;
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        protocol = "wss";
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        url = url.substr(6); //strlen("wss://") == 6
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        upgradeToSecuredConnection();
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    } else if(doestStartsWith(url, "https://")) {
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        defaultPort = 443;
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        protocol = "https";
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        url = url.substr(8); //strlen("https://") == 8
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        upgradeToSecuredConnection();
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    }
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#endif

点击 upgradeToSecuredConnection 找到相关实现，并找到 ESP8266 和 ESP32 对不同证书的处理方法：

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#ifdef ESP8266
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    if(
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            this->_optional_ssl_fingerprint
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        ||   (this->_optional_ssl_rsa_cert && this->_optional_ssl_rsa_private_key)
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        ||   (this->_optional_ssl_ec_cert && this->_optional_ssl_ec_private_key)
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        ||   this->_optional_ssl_trust_anchors
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        ||   this->_optional_ssl_known_key
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    ) {
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        if(this->_optional_ssl_fingerprint) {
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            client->setFingerprint(this->_optional_ssl_fingerprint);
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        }
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        if(this->_optional_ssl_trust_anchors) {
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            client->setTrustAnchors(this->_optional_ssl_trust_anchors);
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        }
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        if(this->_optional_ssl_known_key) {
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            client->setKnownKey(this->_optional_ssl_known_key);
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        }
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        if(this->_optional_ssl_rsa_cert && this->_optional_ssl_rsa_private_key) {
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            client->setClientRSACert(this->_optional_ssl_rsa_cert, this->_optional_ssl_rsa_private_key);
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        }
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        if(this->_optional_ssl_ec_cert && this->_optional_ssl_ec_private_key) {
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            client->setClientECCert(this->_optional_ssl_ec_cert, this->_optional_ssl_ec_private_key);
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        }
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    } else {
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        client->setInsecure();
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    }
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#elif defined(ESP32)
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    if(this->_optional_ssl_ca_cert) {
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        client->setCACert(this->_optional_ssl_ca_cert);
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    }
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    if(this->_optional_ssl_client_ca) {
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        client->setCertificate(this->_optional_ssl_client_ca);
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    }
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    if(this->_optional_ssl_private_key) {
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        client->setPrivateKey(this->_optional_ssl_private_key);
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    }
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#endif

在 ESP32 中没有对无证书的情况进行处理，没有调用过 client->setInsecure();。

将对应代码修改成：

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#elif defined(ESP32)
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    if(
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            this->_optional_ssl_ca_cert
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        ||  this->_optional_ssl_client_ca
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        ||  this->_optional_ssl_private_key
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    ) {
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        if(this->_optional_ssl_ca_cert) {
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            client->setCACert(this->_optional_ssl_ca_cert);
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        }
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        if(this->_optional_ssl_client_ca) {
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            client->setCertificate(this->_optional_ssl_client_ca);
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        }
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        if(this->_optional_ssl_private_key) {
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            client->setPrivateKey(this->_optional_ssl_private_key);
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        }
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    } else {
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        client->setInsecure();
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    }
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#endif

到这里，client->setInsecure(); 会提示报错：类 "websockets::network::SecuredEsp32TcpClient" 没有成员 "setInsecure"C/C++(135)

找到 client 的定义：

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auto client = new WSDefaultSecuredTcpClient;

找到 WSDefaultSecuredTcpClient 的定义：

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#ifndef _WS_CONFIG_NO_SSL
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    // OpenSSL Dependent
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    #define WSDefaultSecuredTcpClient websockets::network::SecuredEsp32TcpClient
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#endif //_WS_CONFIG_NO_SSL

找到 websockets::network::SecuredEsp32TcpClient 的定义：

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namespace websockets { namespace network {
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  typedef GenericEspTcpClient<WiFiClient> Esp32TcpClient;
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  class SecuredEsp32TcpClient : public GenericEspTcpClient<WiFiClientSecure> {
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  public:
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    void setCACert(const char* ca_cert) {
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      this->client.setCACert(ca_cert);
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    }
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    void setCertificate(const char* client_ca) {
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      this->client.setCertificate(client_ca);
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    }
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    void setPrivateKey(const char* private_key) {
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      this->client.setPrivateKey(private_key);
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    }
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  };
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  ...
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}
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}

setInsecure() 的实现可以从 websockets::network::SecuredEsp8266TcpClient 中获取：

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namespace websockets { namespace network {
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  typedef GenericEspTcpClient<WiFiClient> Esp8266TcpClient;
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  class SecuredEsp8266TcpClient : public GenericEspTcpClient<WiFiClientSecure> {
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  public:
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    void setInsecure() {
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      this->client.setInsecure();
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    }
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    ...
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  }
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}
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}

最终的修改结果：

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namespace websockets { namespace network {
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  typedef GenericEspTcpClient<WiFiClient> Esp32TcpClient;
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  class SecuredEsp32TcpClient : public GenericEspTcpClient<WiFiClientSecure> {
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  public:
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    void setCACert(const char* ca_cert) {
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      this->client.setCACert(ca_cert);
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    }
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    void setCertificate(const char* client_ca) {
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      this->client.setCertificate(client_ca);
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    }
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    void setPrivateKey(const char* private_key) {
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      this->client.setPrivateKey(private_key);
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    }
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    void setInsecure() {
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      this->client.setInsecure();
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    }
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  };
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  ...
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}
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}