發送可靠的HTTP請求與Arduino的WiFi客戶端

Question

當我的Arduino MKR1000傳感器被觸發時，我發送一封電子郵件：

//.... 
WiFiClient client; 
char server[] = "www.myserver.com"; 
//.... 

void setup() { 
//... Connect to wifi .... 
} 

void loop() { 
    // when sensor triggered => 
    if (client.connect(server, 80)) { 
     Serial.println("Sending email"); 
     client.print("GET /WaterOff/sendGridCall.php"); 
     client.print("?valve="); 
     client.print(valve); 
     client.print("&position="); 
     client.print(position); 
     client.println(" HTTP/1.1"); 
     client.print("Host: "); 
     client.println(server); 
     client.println("User-Agent: Arduino"); 
     client.println("Connection: close"); 
     client.println(); 
    } 

    delay(6000); 
} 

然而，它不僅工程首幾次（「發送電子郵件」印）之後，它不會執行請求（「發送電子郵件」不會被打印）。我應該採取一些額外的步驟來使其可靠。

Answer 1

您從不關閉連接。但阻止等待電子郵件確認可能會永遠持續下去。你應該考慮一個小型的狀態機來讓你的網絡連接起作用。

void loop() 
{ 
    // when sensor triggered => 
    if (client.connect(server, 80)) {  // You connect to client, but it's already 
              // connected the second time around 
     // send ... 
     // client() should wait for response, and client.disconnect() 
    } 

    // ... 
    delay(6000);  // tip: avoid blocking the main loop, this blocks your ability to 
         // read your sensor while sending emails. 
} 

爲您的應用狀態機看起來是這樣的：

enum EmailState { 
    emIdle, emSendMail, emCheckMailSent, emEmailOK, emEmailError, 
}; 

EmailState email_state; 
unsigned long long mail_timer;  // can be shared between states. 

// small state handlers that do a bit at a time, 
// check for an event, wait on some delay (use millis()) 
// avoid blocking the instruction flow as much as possible. 

static void on_emIdle() 
{ 
    // read sensor, check timer? 
    email_state = (triggered) ? emSendMail : emIdle; 
} 

static void on_sendMail() 
{ 
    if (client.connect()) 
    { 
     // ... prints 
     email_state = emCheckMailSent; 
     return; 
    } 
    email_state = emEmailError; 
} 

static void on_emCheckMailSent() 
{ 
    // receive HTTP response... can have a long timeout without blocking. 
    email_state = emCheckMailSent; 
    // or emEmailOK or emEmailError or retry emSendMail 
} 

static void on_emEmailOK() 
{ 
    if (/*client is connected?*/) 
     client.disconnect(); 

    if (!mail_timer) 
     mail_timer = millis(); 

    if (millis() - mail_timer < 6000) // stay in this state for 6 seconds... 
    { 
     email_state = emEmailOK; 
     return; 
    } 

    mail_timer = 0;  // always reset the timer so it can be used by other states 
    email_state = emIdle; 
} 

static void on_emEmailError() 
{ 
    if (/*client is connected?*/) 
     client.disconnect(); 
    // keep a log ? 
    email_state = emIdle; // or another timer 
} 

//... 
void loop() 
{ 
    // update readings, manage other things... 
    // ... 
    switch(email_state) 
    { 
    default: 
    case emIdle:   on_emIdle();   break; 
    case emSendMail:  on_emSendMail();  break; 
    case emCheckMailSent: on_emCheckMailSent(); break; 
    case emEmailOK:  on_emEmailOK();  break; 
    case emEmailError:  on_emEmailError(); break; 
    } 
}