websocket_client: esp_transport_write() returned -1, transport_error=ESP_ERR_MBEDTLS_SSL_WRITE_FAILED, (IDFGH-16911)

[aiotfactory]

Answers checklist.

• I have read the documentation for esp-protocols components and the issue is not addressed there.
• I have updated my esp-protocols branch (master or release) to the latest version and checked that the issue is present there.
• I have searched the issue tracker for a similar issue and not found a similar issue.

General issue report

I am using ESP-IDF 5.5.1 with esp_websocket_client v1.6.0 to connect to coze.cn (an AI voice agent). The connection is successfully established, and voice calls work normally. However, the connection drops every ~1 minute with errors.

I have consulted Coze's server team, and they confirmed that the server does not actively close connections. Additionally, I have logged the WebSocket Ping/Pong frames, and they appear normal (no missing/failed frames).

E (383448) esp-tls-mbedtls: write error :-0x6C00
E (383448) transport_base: esp_tls_conn_write error, errno=Success
E (383449) transport_ws: Error write header
E (383452) websocket_client: esp_transport_write() returned -1, transport_error=ESP_ERR_MBEDTLS_SSL_WRITE_FAILED, tls_error_code=27648, tls_flags=0, errno=0
E (383465) websocket_coz_chat: event 0 websocket_event_handler error

char *combined_headers = user_malloc(128);	

char *temp_uri = user_malloc(128);	

sprintf(combined_headers,"Authorization: bearer %s\r\n",coz_key);

sprintf(temp_uri,"/v1/chat?bot_id=%s",coz_bot);

esp_websocket_client_config_t ws_cfg = {

    .uri = temp_uri,

    .host = "ws.coze.cn",

    .port = 443,

    .transport = WEBSOCKET_TRANSPORT_OVER_SSL,

    .cert_pem = NULL,

    .reconnect_timeout_ms = 500,

    .network_timeout_ms = 10*1000,

    .buffer_size = 4096,

    .skip_cert_common_name_check = false,

    .headers = combined_headers,

    .keep_alive_enable = true,

    .crt_bundle_attach = esp_crt_bundle_attach,

};

ws_client = esp_websocket_client_init(&ws_cfg);

user_free(combined_headers);

user_free(temp_uri);

esp_websocket_register_events(ws_client, WEBSOCKET_EVENT_ANY, websocket_event_handler, NULL);

esp_websocket_client_start(ws_client);

[aiotfactory]

Here are more logs:

E (125280) esp-tls-mbedtls: write error :-0x6C00
E (125280) transport_base: esp_tls_conn_write error, errno=Connection already in progress
E (125282) transport_ws: Error write header
E (126397) transport_base: poll_write select error 104, errno = Connection reset by peer, fd = 57
E (126397) transport_ws: Error transport_poll_write(-1)
E (126400) websocket_client: esp_transport_write() returned -1, transport_error=ESP_ERR_MBEDTLS_SSL_WRITE_FAILED, tls_error_code=27648, tls_flags=0, errno=0
E (126413) websocket_coz_chat: event 0 websocket_event_handler error
I (126420) websocket_client: Reconnect after 500 ms
W (126424) websocket_coz_chat: event 2 websocket_event_handler disconn
E (126430) websocket_coz_chat: Last error websocket_event_handler error disconn reported from esp-tls: 0x8018
E (126440) websocket_coz_chat: Last error websocket_event_handler error disconn reported from tls stack: 0x6c00
E (126450) websocket_coz_chat: Last error websocket_event_handler error disconn captured as transport's socket errno: 0x68
E (126460) websocket_coz_chat: json sent 1454|-1
I (126466) websocket_coz_chat: websocket_coz_connect...
E (126470) websocket_client: Websocket client is not connected