# 连接错误

连接在线数据库时，至少有两台电脑参与完成这项任务，你的个人电脑和数据库服务器。通常还有很多中介，如 DNS 服务器，代理服务器和防火墙。因此连接在线数据库实际情况很复杂

最基本的问题可能有以下4种：

* [没有互联网连接](/troubleshooting/problems-connecting-to-the-internet.md)
* [找不到主机](/troubleshooting/problems-finding-the-host.md)
* [连不上主机](/troubleshooting/problems-connecting.md)
* [不能和主机通信](/troubleshooting/problems-communicating-with-the-host.md)


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