curl ASSERTs when accessing an LDAP URL

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curl ldap://localhost:1388
curl: result.c:930: try_read1msg: Assertion `!BER_BVISEMPTY( &resoid )' failed.
Aborted (core dumped)

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#!/usr/bin/env python3
"""
Simple socket server that sends a specific binary response on port 1388.
"""

import socket
import logging
import sys

# Set up logging
logging.basicConfig(level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')
log = logging.getLogger(__name__)

# The binary response to send
BINARY_RESPONSE = b'0%1\x01\x00x\x00\r\x00\x00\x00\x00\x00\x8a\x00\r\x00\x06\x00\r\x00\x00\x00\r\x00\x00\x00\x00\xc7\xc7\xc7\x9b\x80\xeb\x05123456\x00\x03\x00\x00\x00\tcn=d\x00\x10man'

PORT = 1388

def handle_client(client_socket, client_address):
    """Handle a single client connection."""
    try:
        log.info(f"Client connected from {client_address}")

        # Send the binary response
        client_socket.send(BINARY_RESPONSE)
        log.info(f"Sent {len(BINARY_RESPONSE)} bytes to {client_address}")

    except Exception as e:
        log.error(f"Error handling client {client_address}: {e}")
    finally:
        # Close the client socket
        client_socket.close()
        log.info(f"Connection closed for {client_address}")

def run_server():
    """Run the socket server."""
    # Create a socket
    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    # Allow socket reuse
    server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

    try:
        # Bind to the port
        server_socket.bind(('localhost', PORT))
        server_socket.listen(5)

        log.info(f"Server listening on port {PORT}")
        log.info("Press Ctrl+C to stop the server")

        while True:
            try:
                # Accept a client connection
                client_socket, client_address = server_socket.accept()

                # Handle the client in the same thread (simple approach)
                handle_client(client_socket, client_address)

            except KeyboardInterrupt:
                log.info("Server shutdown requested")
                break
            except Exception as e:
                log.error(f"Error accepting connection: {e}")

    except Exception as e:
        log.error(f"Error starting server: {e}")
        sys.exit(1)
    finally:
        server_socket.close()
        log.info("Server socket closed")

if __name__ == "__main__":
    run_server()

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curl ldap://localhost:1388
curl: result.c:930: try_read1msg: Assertion `!BER_BVISEMPTY( &resoid )' failed.
Aborted (core dumped)

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docker run -it -v $PWD/socket_server.py:/tmp/socket_server.py ubuntu:latest 
...
export DEBIAN_FRONTEND=noninteractive
apt update >/dev/null 2>&1
apt install -y curl python3 >/dev/null 2>&1
python3 /tmp/socket_server.py &
curl ldap://localhost:1388

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$ docker run -it -v $PWD/socket_server.py:/tmp/socket_server.py ubuntu:latest 
root@f68274eeed75:/# export DEBIAN_FRONTEND=noninteractive
root@f68274eeed75:/# apt update >/dev/null 2>&1 
root@f68274eeed75:/# apt install -y curl python3 >/dev/null 2>&1
root@f68274eeed75:/# python3 /tmp/socket_server.py &
[1] 3113
root@f68274eeed75:/# 2025-07-17 19:56:23,952 - INFO - Server listening on port 1388
2025-07-17 19:56:23,952 - INFO - Press Ctrl+C to stop the server

root@f68274eeed75:/# curl ldap://localhost:1388
2025-07-17 19:56:44,348 - INFO - Client connected from ('127.0.0.1', 52256)
2025-07-17 19:56:44,349 - INFO - Sent 56 bytes to ('127.0.0.1', 52256)
2025-07-17 19:56:44,349 - INFO - Connection closed for ('127.0.0.1', 52256)
curl: ../../../../libraries/libldap/result.c:945: try_read1msg: Assertion `!BER_BVISEMPTY( &resoid )' failed.
Aborted (core dumped)
root@f68274eeed75:/#

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curl ldap://localhost:1388
curl: result.c:952: try_read1msg: Assertion `!BER_BVISEMPTY( &resoid )' failed.
[1]    43669 IOT instruction (core dumped)  curl ldap://localhost:1388

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curl: (52) Received malformed LDAP message from server.