WiFiClient::flush() is blocked when using httpClient.post some time.

[lzw7603]

Hardware:

Board: ESP32 Dev Module Core Installation/update date: 9/9/2018 IDE name: Arduino IDE Flash Frequency: 80Mhz Upload Speed: 921600

Description:

1. web server is tomcat 8.5.31
2. os is debian 9
3. runing in Docker

Sketch:

//Change the code below by your sketch
#include <Arduino.h>

String httpPost(const char *pUrl, char *pBuf, int& nCode)
{
    //check
    if(WiFi.status() != WL_CONNECTED) return "";

    //init
    HTTPClient http;
    String payload;

    //http pos
    http.begin(pUrl); //HTTP
    //http.setTimeout(3000);
    http.addHeader("content-type", "application/json");

    // start connection and send HTTP header
    Serial.print("[HTTP] GET...\n");
    int httpCode = http.POST((uint8_t*)pBuf, strlen(pBuf));

    // httpCode will be negative on error
    if(httpCode > 0) 
    {
        // HTTP header has been send and Server response header has been handled
        Serial.printf("[HTTP] GET... code: %d\n", httpCode);

        // file found at server
        if(httpCode == HTTP_CODE_OK) {
            payload = http.getString();
            Serial.println(payload);
        }
    } else {
        Serial.printf("[HTTP] GET... failed, error: %s\n", http.errorToString(httpCode).c_str());
    }

    //last
    http.end();
    nCode = httpCode;
    return payload;
}

void setup() {
    //init serial
    Serial.begin(115200);

    //init wifi
    WiFi.mode(WIFI_STA);
    WiFi.begin("LESSO",  "");
    while (WiFi.waitForConnectResult() != WL_CONNECTED) {
      Serial.println(".");
      delay(5000);
    }

    char buf[100];
    memset(buf, 0x00, 100 * sizeof(char));
    sprintf(buf, "{\"devID\":\"%s\"}", g_chipID);
    Serial.println(buf);

    //send online
    int nCode = 0;
    String strJson = httpPost("http://192.168.3.197:49315/upload-file/getUpdateInfo", buf, nCode);
    Serial.println("good!!");
}

void loop() {
}

First time, i found that is block on line 688 in file HTTPClient.cpp

String HTTPClient::getString(void)
{
    StreamString sstring;
    if(_size) {
        // try to reserve needed memmory
        if(!sstring.reserve((_size + 1))) {
            log_d("not enough memory to reserve a string! need: %d", (_size + 1));
            return "";
        }
    }
    writeToStream(&sstring); // <------------- block here
    return sstring;
}

And then I found that is block on line 668 in file HTTPClient.cpp

int HTTPClient::writeToStream(Stream * stream)
{
   ......
    end();  // <------------- block here, the last 2 line
    return ret;
}

And then I found that is block on line 235 in file HTTPClient.cpp

void HTTPClient::end(void)
{
    if(connected()) {
        if(_tcp->available() > 0) {
            log_d("still data in buffer (%d), clean up.", _tcp->available());
            _tcp->flush(); // <------------- block here
        }
        ......
    } else {
        log_v("tcp is closed");
    }
}

And then I found that is block on line 425 in file WiFiClient.cpp

void WiFiClient::flush() {
    ......
    while(a){
        toRead = (a>WIFI_CLIENT_FLUSH_BUFFER_SIZE)?WIFI_CLIENT_FLUSH_BUFFER_SIZE:a;
        res = recv(fd(), buf, toRead, MSG_DONTWAIT); // <------------- block here
        if(res < 0) {
            log_e("%d", errno);
            stop();
            break;
        }
        a -= res;
    }
    free(buf);
}

java code on server

@Controller
public class UpdateController {

    @Autowired
    private UpdateService updateService;

    @RequestMapping("getUpdateInfo")
    @ResponseBody
    public Object getUpdateInfo(HttpServletRequest request, @RequestBody String json) {
        // {"devID":"", "IP":"", "Ver":"", "update":""}
        //" {\"devID\":\"%s\", \"IP\":\"%s\", \"Ver\":\"%s\", \"update\":\"%d\"}"
        JSONObject machineInfo = JSONObject.parseObject(json);
        String devID = machineInfo.getString("devID");
        Object returnJson = updateService.getUpdateInfo(devID);
        return returnJson;
    } 
}

[hpsaturn]

Hi, I have a possible similar behavior with last version of HTTPClient.

My code use a InfluxDB Library, the implementation there is:

bool InfluxArduino::write(const char *measurement,const char *tagString,const char *fieldString)
{   
    HTTPClient http;
    char uri[32];
    sprintf(uri, "/write?db=%s", _database);

    if(_isSecure)
    {
       http.begin(_host, _port, uri, _cert);
    }
    else
    {
        http.begin(_host, _port, uri);
    }
    http.addHeader("Content-Type", "text/plain"); // not sure what influx is looking for but this works?

    if(_isAuthorised)
    {
        http.setAuthorization(_username,_password);
    }

    char writeBuf[512]; // ¯\_(ツ)_/¯ 
    if(strlen(tagString) > 0)
    {
        sprintf(writeBuf,"%s,%s %s",measurement,tagString,fieldString); //no comma between tags and fields
    }

    else
    {
        //no tags
        sprintf(writeBuf,"%s %s",measurement,fieldString); //no comma between tags and fields
    }
    if(debug) Serial.println(writeBuf);
    _latestResponse = http.POST(writeBuf);
    http.end();
    return _latestResponse == 204;
}

after some hours, this enter to a internal loop on HTTPClient and it stays there, because other functions in my code works, like Bluetooth callbacks and Bluetooth advertising

I have the next frameworks versions in my platformio installation:

    "framework-arduinoespressif32": {
      "type": "framework",
      "optional": true,
      "version": "~2.10002.190416"
    },
    "framework-espidf": {
      "type": "framework",
      "optional": true,
      "version": "~3.30200.190418"
    }

and espressif32 Version: 1.8.0

My project libraries:

Updating Adafruit AM2320 sensor library  @ 1.1.1          [Up-to-date]
Updating Adafruit BME680 Library         @ 1.0.7          [Up-to-date]
Updating Adafruit Unified Sensor         @ 1.0.3          [Up-to-date]
Updating ArduinoJson                     @ 6.10.1         [Up-to-date]
Updating ClosedCube BME680               @ 1.2.0          [Up-to-date]
Updating HPMA115S0 Arduino Library       @ 23cbd44        [Up-to-date]
Updating Influx-Arduino                  @ ce16fc3        [Up-to-date]
Updating U8g2                            @ 2.26.5         [Up-to-date]

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