WebSocket Second Response Contains Invalid Data Causing SDK Error

[Ilya-Vys]

Hi all!
I am experiencing an issue in our mobile application when establishing a WebSocket connection. I start a timer that sends a short command (b1000_0) at an interval of n seconds to request data. While the first response returns valid data, the second response does not, leading my SDK to throw an error during processing and subsequently close the connection.

This issue is not limited to the b1000_0 command; similar behavior is observed with each other requests as well—always, the first response is valid, and the second response is invalid.

My connection request and response headers:
Request Headers user-agent: [Dart/3.6 (dart:io)]connection: [Upgrade]cache-control: [no-cache]accept-encoding: [gzip]content-length: [0]sec-websocket-version: [13]host: [...]sec-websocket-extensions: [permessage-deflate; server_no_context_takeover; client_max_window_bits=9]sec-websocket-key: [....]sec-websocket-protocol: [zap-protocol-v1]upgrade: [websocket]

Response Headers connection: [upgrade]date: [Mon, 10 Feb 2025 11:22:39 GMT]sec-websocket-version: [13]sec-websocket-extensions: [permessage-deflate; server_no_context_takeover; client_max_window_bits=9]sec-websocket-protocol: [zap-protocol-v1]server: [nginx]upgrade: [websocket]sec-websocket-accept: [...]

Valid data taken(1 request):
["0xc1", "0x5a", "0x44", "0x8b", "0x4d", "0xa", "0x80", "0x20", "0x14", "0x6", "0xef", "0xf2", "0xd1", "0x52", "0x42", "0x2c", "0x10", "0xba", "0x8c", "0xd8", "0xcb", "0x40", "0xe8", "0x47", "0x52", "0xa1", "0x10", "0xef", "0xde", "0xab", "0x16", "0xed", "0x66", "0x6", "0xa6", "0x60", "0xb4", "0x8b", "0xdd", "0xc8", "0x61", "0x28", "0x3f", "0x42", "0x77", "0xaa", "0xed", "0x35", "0x4", "0x26", "0x17", "0xf6", "0xe8", "0x13", "0x27", "0xd9", "0x4a", "0xc9", "0x21", "0xae", "0xd1", "0xd0", "0x9e", "0x37", "0x4e", "0x52", "0xc0", "0x12", "0x99", "0x74", "0x5", "0x5e", "0x94", "0x0", "0xe5", "0xc3", "0xf8", "0xe9", "0xc5", "0x70", "0xb8", "0xd9", "0x9f", "0x7c", "0x35", "0xcf", "0x92", "0xe7", "0x4f", "0x50", "0xeb", "0xd"]
Invalid data taken(2 request)
["0xc1", "0x6", "0xaa", "0xa6", "0xb3", "0x7d", "0x0", "0x0"]

In this simple example, the second request returns significantly less data than expected – it should return roughly the same amount. When requesting heavier objects sized 300–400 bytes, the second request returns 5–10 bytes less. What could be the potential reasons for this behavior?

[fuzqing]

What did you do? If possible, provide a simple script for reproducing the error.

What version of Workerman are you using?

This might answer your question: #1052 (comment)