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websocket.c example: curl_ws_recv returns "Socket not ready for send/recv" (errno 81) #13288

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untitaker opened this issue Apr 4, 2024 · 1 comment · May be fixed by #14214
Open

websocket.c example: curl_ws_recv returns "Socket not ready for send/recv" (errno 81) #13288

untitaker opened this issue Apr 4, 2024 · 1 comment · May be fixed by #14214
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@jay
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@untitaker
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untitaker commented Apr 4, 2024 •
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I did this

  1. copied this example into foo.c
  2. edited the websocket URL in foo.c to be a valid websocket server. wss://ws.postman-echo.com/raw works, ws://localhost:8080 works as well, with websocat being invoked as websocat -s 8080
  3. cloned curl master, moved foo.c into root folder
  4. cmake -DENABLE_WEBSOCKETS=on
  5. make
  6. cc -L lib/ foo.c -lcurl
  7. LD_LIBRARY_PATH=lib/ ./a.out

I expected the following

some kind of ping-pong demo, or a hanging connection, depending on which websocket server is being used.

instead the program immediately quits with this after sending the initial HTTP headers:

ws: curl_ws_recv returned 81, received 0

in the real-world application that is built based on that example code, I get (just posting the strerror for searchability):

code 81: "Socket not ready for send/recv"

curl/libcurl version

git sha 376cd67

I thought this was related to #11443, so I checked curl 7 as well. On tag curl-7_88_1 (046209e), foo.c hangs instead, though websocket.c does not exist on that commit at all anyway

operating system

Ubuntu 23.10
@untitaker
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untitaker commented Apr 4, 2024 •
edited
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Dug around a little, and I suspect that this is intended behavior due to #10625, and it's just the example that needs updating, similar to #10760

though I'm not sure a crude busy-loop is a good example to follow either

@jay jay self-assigned this Jul 1, 2024
jay added a commit to jay/curl that referenced this issue Jul 17, 2024
@jay
docs/examples/websocket: fix "socket not ready" on recv
732da22 
- Overhaul the recv_any function to block waiting for a complete
  websocket message from the server.

- Have recv_pong and recv_header call recv_any to retrieve a complete
  message, rather than duplicate the efforts in each function.

- Fix sleep() macro for Windows to treat the parameter as seconds
  instead of milliseconds.

- Improve documentation of curl_ws_recv/send to better explain
  CURLE_AGAIN behavior.

- Use echo.websocket.org instead of example.com as the example websocket
  server since it is a server the example actually works on.

recv_any now calls curl_ws_recv repeatedly, waiting until the socket is
readable and a full websocket message is read from the server.

Prior to this change the example did not handle the non-blocking
behavior of curl_ws_recv. When curl_ws_recv returned CURLE_AGAIN the
example would fail with "socket not ready".

Fixes curl#13288
Closes #xxxx
jay added a commit to jay/curl that referenced this issue Jul 17, 2024
@jay
docs/examples/websocket: fix "socket not ready" error
ba5cc0b 
- Add function blocking_ws_recv which blocks waiting for a complete
  websocket message from the server.

blocking_ws_recv calls curl_ws_recv repeatedly, waiting until the socket
is readable and a full websocket message is read from the server.

Prior to this change the example failed when curl_ws_recv returned
CURLE_AGAIN.

Fixes curl#13288
Closes #xxxx
@jay jay linked a pull request Jul 17, 2024 that will close this issue
Open
jay added a commit to jay/curl that referenced this issue Jul 19, 2024
@jay
docs/examples/websocket: fix "socket not ready" on recv
1b9230e 
- Overhaul the recv_any function to block waiting for a complete
  websocket message from the server.

- Have recv_pong and recv_header call recv_any to retrieve a complete
  message, rather than duplicate the efforts in each function.

- Fix sleep() macro for Windows to treat the parameter as seconds
  instead of milliseconds.

- Improve documentation of curl_ws_recv/send to better explain
  CURLE_AGAIN behavior.

- Use echo.websocket.org instead of example.com as the example websocket
  server since it is a server the example actually works on.

recv_any now calls curl_ws_recv repeatedly, waiting until the socket is
readable and a full websocket message is read from the server.

Prior to this change the example did not handle the non-blocking
behavior of curl_ws_recv. When curl_ws_recv returned CURLE_AGAIN the
example would fail with "socket not ready".

Fixes curl#13288
Closes #xxxx
jay added a commit to jay/curl that referenced this issue Aug 4, 2024
@jay
docs/examples/websocket: fix "socket not ready" on recv
21a8485 
- Overhaul the recv_any function to block waiting for a complete
  websocket message from the server.

- Have recv_pong and recv_header call recv_any to retrieve a complete
  message, rather than duplicate the efforts in each function.

- Fix sleep() macro for Windows to treat the parameter as seconds
  instead of milliseconds.

- Improve documentation of curl_ws_recv/send to better explain
  CURLE_AGAIN behavior.

- Use echo.websocket.org instead of example.com as the example websocket
  server since it is a server the example actually works on.

recv_any now calls curl_ws_recv repeatedly, waiting until the socket is
readable and a full websocket message is read from the server.

Prior to this change the example did not handle the non-blocking
behavior of curl_ws_recv. When curl_ws_recv returned CURLE_AGAIN the
example would fail with "socket not ready".

Fixes curl#13288
Closes #xxxx
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docs/examples/websocket: fix "socket not ready" on recv jay/curl
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