http: response dropped when client half-closes after sending request (request still executed) #36454

Is there an existing issue for this?

• I have searched the existing issues

Current behaviour

With the new HTTP server (#35182), if a client sends a complete request and then half-closes its write side (shutdown(SHUT_WR), i.e. sends FIN), the server closes the connection without writing a response. The request is still executed.

Some tools (nc -N, socat) rely on it. Was the change intentional?

This was found while testing v32.0rc

Expected behaviour

The server should write the response and then close, as v31 (libevent) did.

Steps to reproduce

bitcoind -regtest -daemon
python3 -c '
  import socket, sys
  s = socket.create_connection(("127.0.0.1", 18443))
  s.sendall(b"GET / HTTP/1.1\r\nHost: x\r\n\r\n")
  s.shutdown(socket.SHUT_WR)
  while (d := s.recv(4096)): sys.stdout.buffer.write(d)
'

This on v32rc gives no output.

On v31 it does:

Bitcoin Core starting
HTTP/1.1 405 Method Not Allowed
Date: Wed, 07 Oct 2026 18:57:26 GMT
Content-Length: 41
Content-Type: text/html; charset=ISO-8859-1

JSONRPC server handles only POST requests⏎ 

Relevant log output

No response

How did you obtain Bitcoin Core

Compiled from source

What version of Bitcoin Core are you using?

9dfde64cc3262329051fd05fffe40eecc786a99f

Operating system and version

Arch Linux, kernel 7.1.8-arch1-3

Machine specifications

No response

Thanks, would this be solved by #35780 ?

that was a fast reply :). Tried #35780, but it doesn't solve this

I followed the reproduce steps and on v32.0rc there was no output , on v31 i got the following output

HTTP/1.1 405 Method Not Allowed
Date: Wed, 07 Oct 2026 21:24:35 GMT
Content-Length: 41
Content-Type: text/html; charset=ISO-8859-1

JSONRPC server handles only POST requests

I tried adding a check in HTTPRemoteClient::MaybeDisconnect that checks if the client is marked for disconnect while a request is still running or a reply is still queued and then keeps the connection until a reply is sent.

if (m_disconnect && (m_req_busy || ReadyToSend())) return false;

Here is the link to the commit i made http: send reply before disconnect on client half-close

Is this approach acceptable? I have tested it out and it returned the response below instead of a blank output after running this test. Test run:

bitcoind -regtest -daemon

python3 -c '
import socket, sys
s = socket.create_connection(("127.0.0.1", 18443))
s.sendall(b"GET / HTTP/1.1\r\nHost: x\r\n\r\n")
s.shutdown(socket.SHUT_WR)
while (d := s.recv(4096)): sys.stdout.buffer.write(d)
'

Output: Bitcoin Core starting

HTTP/1.1 405 Method Not Allowed
Date: Wed, 07 Oct 2026 23:06:48 GMT
Content-Length: 41
Content-Type: text/html; charset=ISO-8859-1

JSONRPC server handles only POST requests