# requests.exceptions.ConnectionError: HTTPConnectionPool(host='slow.example.com', port=80): 超过最大重试次数 (由ConnectTimeoutError('<urllib3.connection.HTTPConnection object at 0x...>: 无法建立新连接：[Errno 110] 连接超时')引起)

- **ID:** `python/requests-connectionerror-timeout-connect`
- **领域:** python
- **类别:** network_error
- **验证级别:** ai_generated
- **修复率:** 80%

## 根因

由于网络问题、防火墙或服务器宕机，服务器不可达。

## 版本兼容性

| 版本 | 状态 | 引入 | 弃用 |
|------|------|------|------|
| 3.x | active | — | — |

## 解决方案

1. **Check network connectivity using ping or traceroute** (80% 成功率)
   ```
   ping slow.example.com
# If unreachable, check firewall or VPN settings
   ```
2. **Use a different network interface or proxy** (70% 成功率)
   ```
   proxies = {'http': 'http://proxy.example.com:8080'}
requests.get('http://slow.example.com', proxies=proxies)
   ```

## 无效尝试

- **Reducing the timeout value to fail faster** — Does not solve the connectivity issue. (80% 失败率)
- **Using a different user-agent** — The problem is network-level, not application-level. (95% 失败率)