[34415056][E][WiFiClientImpl.h:468] tcpWrite(): fail on fd 49, errno: 128, "Socket is not connected"

[UnknownKhan2023]

Chip used ESP32 :

Problem 1 :
After starting ESP32, all worked well, left overnight and then I found this error at the morning

[34415056][E][WiFiClientImpl.h:468] tcpWrite(): fail on fd 49, errno: 128, "Socket is not connected"

• Stream "No callback" example is used.
• Getting stream data correctly, but the above error happens when trying to write to the server using setString() method right after getting stream data
• stream.httpConnected() returns true.

Problem 2 :
setStringAsync() writes the previous operation to the server, and saves the current operation for the next call.

How to solve these problem?

[mobizt]

You should allow the idle time for stream to be connected.

You should use different FirebaseData objects for stream and non-stream operations.

There is no memory limit after v4 which you can define more FirebaseData objects to use in ESP32.

For async function, I'm not sure you understand what is it designed for.

The async function is not actually asynchronous operation unless the server response was ignored then, no changes in data stored in FirebaseData object.

I'm not recommend using async function.

The next version (v5) almost functions removed and changed and will allow you to use the library without using FirebaseData objects with true asynchronous operation support.

[UnknownKhan2023]

• Stream operation has no issue,

• Used two different firebaseData object to stream and non-stream operations.

• non-stream operations Like Switch(); continue to show the above error.

• async function removed and setString() works well. No problem.

// Define Firebase Data object
FirebaseData stream;
FirebaseData fbdo;

void InternetDataReceived() {
  if (isStreamAvailable) {
    isStreamAvailable = false;

      if (String(stream.dataPath()) == "/Items/Relay1/State") {
        if (AppRequest == "0") {
          relayOnOff(1, false, "streamCallback", false);
        } else {
          relayOnOff(1, true, "streamCallback", false);
        }
      }

      if (String(stream.dataPath()) == "/Items/Relay1/ESPResponse") {
        Firebase.RTDB.setString(&fbdo, "/USERS/0123456789/Devices/Board1/Items/Relay1/State", ReceivedData);
      }
}

void Switch() {
 if (SwitchCurrentState_1 != !digitalRead(SwitchPin1)) {
    Firebase.RTDB.setString(&fbdo, "/USERS/0123456789/Devices/Board1/Items/Relay1/State", !SwitchCurrentState_1 );
}

void loop() {
  if (stream.streamAvailable()) {
    isStreamAvailable = true;
  }
  InternetDataReceived();
  void Switch();
}

[mobizt]

You never follow the library examples.

Please read the comment in examples carefully to use library correctly.

You should know what the required thing is missing especially in loop.

[UnknownKhan2023]

I didnt write the whole code: Loop section contains 100 lines of code, so i wrote the sample code,
Below is the full code

if (!Firebase.ready())
return;

if (!Firebase.RTDB.readStream(&stream))
Serial.printf("sream read error, %s\n\n", stream.errorReason().c_str());

if (stream.streamTimeout())
Serial.println("stream timeout, resuming...\n");

if (stream.streamAvailable()) {
isStreamAvailable = true;
}

[mobizt]

As you wrote.

Stream "No callback" example is used.

You should debug your code and check for network, internet and free memory.

I can't help to debug your code.

[UnknownKhan2023]

• I have no problem with the stream operation
• Problem is only with the non stream operation,
• at the beginning of the esp32 starts, setString() operation works well.
• But after 2-3 hours setString() operation showing the error
  [34415056][E][WiFiClientImpl.h:468] tcpWrite(): fail on fd 49, errno: 128, "Socket is not connected"

at that time

• stream.httpConnected() returns true.
• Wifi is connected properly
• Stream operation is also working perfectly

I just want to solve this

[mobizt]

As I said you should debug your code.

It's your device and code.

The error "Socket is not connected" is from the WiFiClient that means network connection drops.

Do not rely on stream.httpConnected() as it is always returns true until timed out occurred.

You should use ping to check internet access.

[UnknownKhan2023]

If network connection drops causing the problem, Then, How does stream operation working well with no problem?
How to reconnect to socket when "Socket is not connected"?

[mobizt]

How does stream operation working well with no problem?

It is not true as stream is one way communication SSE, the server connection is just kept open but no guarantee that sever is alive.

Library will look for keep-alive event data and use as heartbeat signal to determine that server is alive.

[UnknownKhan2023]

Previous version of the library had no issue, after updating the latest version I found this

[mobizt]

Nothing is related to the version of library.

The problem is internet access problem.

[mobizt]

Library was tested intensively 24/7 for months after v4 released in all networks (GSM, Ethernet and WiFi) and devices and it works well.

[UnknownKhan2023]

Please help me
How to reconnect to socket when "Socket is not connected"?

[mobizt]

That's your network and internet problems.

I can do nothing.

[mobizt]

At this moment, I still test it and it works well.

[mobizt]

You can force internal WiFiClient to stop anytime when you get the network issue like that with
fbdo.stopWiFiClient();

[UnknownKhan2023]

You accept it or not, I have no issue with v4.3.20. Loving it, and using it currently.

But, with v4.4.x versions, even uploading the exact "no callback" example (ino file is untouched),

• sometime, [WiFiClientImpl.h:468] tcpWrite(): fail on fd 49, errno: 128, "Socket is not connected" this error occurs for non stream objects
• sometime, no automatic reconnection to the server happens for both, stream & non-stream objects.
• sometime, connected to internet, but "stream read error" happens in never ending loop.

v4.3.20 auto reconnect successfully in all possible situations.

Can you explain why v4.3.20 has no issue but v4.4.x failed in some situations and never auto reconnect itself? (exact "no callback" example used in both situations)

[mobizt]

That is your assumption based on your environment.

The v4.4.x is big update and improvement in memory, speed and reliability.

We use Client (Eyhernet, WiFI and GSM) with BearSSL for all platforms instead of relying on WiFiClientSecure which in ESP32 it is based on mbedTLS.

I already said about the test which I have done intensively even this moment.

There is no network reconnection issue in v4.4.x. The WiFiClientImpl.h is the replacement of original WiFiClient core library which has a multitasking bug when running in FreeRTOS task which nobody from ESP32 Arduino team addressed this issue.

The error "Socket is not connected" is the WiFiClient bugs too that the peer connection drops unexpectedly, and this bugs also remain in WiFiClientImpl.h too.

The "stream read error" is related to this socket error that WiFiClient has technically bug for socket reading loop without exit when this error happened.

This situation is rarely found when server closed the connection unexpectedly and raised the WiFiClient bug.

Ofcourse, this issue was not found in the older version because it used WiFiClientSecure instead of WiFiClient.

That is why I recommend forcing the WiFiClient to stop or reconnect WiFi (with code) when you get this situation.
 
I will fix this in the next update or recommend using this new async version (when it is available)

[UnknownKhan2023]

Thanks a lot for your supports. That's I love most.
Thanks again for this great library

[yapyinghao]

Hi, i am facing the same issue as well when i use
->Firebase.RTDB.setBool(&fbdoWrite, path, false)
only have this problem after performing this function call for few times. Intermittent. Please advise if you found any fix @UnknownKhan2023 . Thanks for the great library as always @mobizt .

[mobizt]

There is nothing to fix and it's not the issue in normal use (non-stream). You should debug your code first.