python network_error ai_generated true

aiohttp.client_exceptions.ClientConnectorError: Cannot connect to host api.example.com:443 ssl:default [Connect call failed]

ID: python/aiohttp-cannot-connect-to-host

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-07-02First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.8 active — — —
3.9 active — — —
3.10 active — — —
3.11 active — — —

Root Cause

DNS resolution or TCP connection to the target host failed, often due to network restrictions, wrong host/port, or firewall blocking outbound traffic.

generic

中文

对目标主机的 DNS 解析或 TCP 连接失败，通常因网络限制、错误的主机/端口或防火墙阻止出站流量。

Workarounds

  1. 90% success 
    Configure a proxy if the environment requires one:

async with aiohttp.ClientSession() as s:
    async with s.get(url, proxy='http://proxy.local:8080') as r:
        ...
  2. 85% success 
    Verify DNS and connectivity first:

import socket
socket.gethostbyname('api.example.com')
# then retry with aiodns resolver if needed

Dead Ends

Common approaches that don't work:

  1. 80% fail

    Connection is refused or unreachable; a longer timeout only delays the same error.

  2. 85% fail

    The failure occurs before the TLS handshake; ssl=False does not help when TCP connect fails.