通过 fsockopen 函数发送数据，如何实现 socket 的数据传输？有哪些技巧？

gitbox 2025-06-21

在 PHP 中，fsockopen 函数是一个常用的用于创建套接字连接的函数，它允许你与远程服务器进行数据通信。通过 fsockopen，你可以实现简单的 socket 数据传输，这对于需要低级网络操作的应用程序来说非常有用。本文将探讨如何使用 fsockopen 实现数据传输，并分享一些在使用过程中可能会用到的技巧。

1. fsockopen 函数基本使用

fsockopen 函数用于打开一个网络连接，可以用来创建 TCP 或 UDP 套接字。最基本的函数原型如下：

<span><span>resource </span><span><span class="hljs-title function_ invoke__">fsockopen</span></span><span> ( </span><span><span class="hljs-keyword">string</span></span><span> </span><span><span class="hljs-variable">$hostname</span></span><span> , </span><span><span class="hljs-keyword">int</span></span><span> </span><span><span class="hljs-variable">$port</span></span><span> [, </span><span><span class="hljs-keyword">int</span></span><span> &amp;</span><span><span class="hljs-variable">$errno</span></span><span> [, </span><span><span class="hljs-keyword">string</span></span><span> &amp;</span><span><span class="hljs-variable">$errstr</span></span><span> [, </span><span><span class="hljs-keyword">float</span></span><span> </span><span><span class="hljs-variable">$timeout</span></span><span> = </span><span><span class="hljs-title function_ invoke__">ini_get</span></span><span>(</span><span><span class="hljs-string">"default_socket_timeout"</span></span><span>) ]]] )
</span></span>

$hostname：目标主机名或 IP 地址。
$port：目标端口号。
$errno 和 $errstr：可选的参数，用来捕获错误信息。
$timeout：可选的连接超时时间，单位为秒。

一个简单的使用例子：

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$host</span></span><span> = </span><span><span class="hljs-string">'www.example.com'</span></span><span>;
</span><span><span class="hljs-variable">$port</span></span><span> = </span><span><span class="hljs-number">80</span></span><span>;
</span><span><span class="hljs-variable">$timeout</span></span><span> = </span><span><span class="hljs-number">30</span></span><span>; </span><span><span class="hljs-comment">// 设置超时时间为 30 秒</span></span><span>

</span><span><span class="hljs-comment">// 使用 fsockopen 建立连接</span></span><span>
</span><span><span class="hljs-variable">$socket</span></span><span> = </span><span><span class="hljs-title function_ invoke__">fsockopen</span></span><span>(</span><span><span class="hljs-variable">$host</span></span><span>, </span><span><span class="hljs-variable">$port</span></span><span>, </span><span><span class="hljs-variable">$errno</span></span><span>, </span><span><span class="hljs-variable">$errstr</span></span><span>, </span><span><span class="hljs-variable">$timeout</span></span><span>);

</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-variable">$socket</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"错误： <span class="hljs-subst">$errno</span></span></span><span> - </span><span><span class="hljs-subst">$errstr</span></span><span>&lt;br /&gt;\n";
} </span><span><span class="hljs-keyword">else</span></span><span> {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"成功连接到 <span class="hljs-subst">$host</span></span></span><span>:</span><span><span class="hljs-subst">$port</span></span><span>&lt;br /&gt;\n";
    </span><span><span class="hljs-title function_ invoke__">fclose</span></span><span>(</span><span><span class="hljs-variable">$socket</span></span><span>);
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

2. 使用 fsockopen 进行数据传输

一旦连接建立，你就可以开始与服务器进行数据传输。对于 HTTP 协议的通信，通常你需要发送一个请求头，服务器将响应相应的数据。以下是一个简单的 HTTP 请求示例：

<span><span><span class="hljs-meta">&lt;?php</span></span><span>
</span><span><span class="hljs-variable">$host</span></span><span> = </span><span><span class="hljs-string">'www.example.com'</span></span><span>;
</span><span><span class="hljs-variable">$port</span></span><span> = </span><span><span class="hljs-number">80</span></span><span>;
</span><span><span class="hljs-variable">$timeout</span></span><span> = </span><span><span class="hljs-number">30</span></span><span>;

</span><span><span class="hljs-variable">$socket</span></span><span> = </span><span><span class="hljs-title function_ invoke__">fsockopen</span></span><span>(</span><span><span class="hljs-variable">$host</span></span><span>, </span><span><span class="hljs-variable">$port</span></span><span>, </span><span><span class="hljs-variable">$errno</span></span><span>, </span><span><span class="hljs-variable">$errstr</span></span><span>, </span><span><span class="hljs-variable">$timeout</span></span><span>);

</span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-variable">$socket</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"错误： <span class="hljs-subst">$errno</span></span></span><span> - </span><span><span class="hljs-subst">$errstr</span></span><span>&lt;br /&gt;\n";
} </span><span><span class="hljs-keyword">else</span></span><span> {
    </span><span><span class="hljs-comment">// 构建 HTTP 请求头</span></span><span>
    </span><span><span class="hljs-variable">$request</span></span><span> = </span><span><span class="hljs-string">"GET / HTTP/1.1\r\n"</span></span><span>;
    </span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"Host: <span class="hljs-subst">$host</span></span></span><span>\r\n";
    </span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"Connection: close\r\n"</span></span><span>;
    </span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"\r\n"</span></span><span>;

    </span><span><span class="hljs-comment">// 发送请求</span></span><span>
    </span><span><span class="hljs-title function_ invoke__">fwrite</span></span><span>(</span><span><span class="hljs-variable">$socket</span></span><span>, </span><span><span class="hljs-variable">$request</span></span><span>);

    </span><span><span class="hljs-comment">// 接收并输出服务器响应</span></span><span>
    </span><span><span class="hljs-keyword">while</span></span><span> (!</span><span><span class="hljs-title function_ invoke__">feof</span></span><span>(</span><span><span class="hljs-variable">$socket</span></span><span>)) {
        </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-title function_ invoke__">fgets</span></span><span>(</span><span><span class="hljs-variable">$socket</span></span><span>, </span><span><span class="hljs-number">128</span></span><span>);
    }

    </span><span><span class="hljs-title function_ invoke__">fclose</span></span><span>(</span><span><span class="hljs-variable">$socket</span></span><span>);
}
</span><span><span class="hljs-meta">?&gt;</span></span><span>
</span></span>

在上述代码中，我们使用 fsockopen 建立连接，然后通过 fwrite 函数将 HTTP 请求头发送到服务器，并使用 fgets 函数读取服务器返回的数据。最后，通过 fclose 关闭套接字连接。

3. 常见技巧与注意事项

3.1 设置超时

在网络编程中，设置合理的超时时间非常重要，特别是当你与远程服务器进行交互时。可以通过 fsockopen 的 $timeout 参数来控制连接的超时。如果你设置的超时过短，可能会导致连接过早中断；过长则可能让程序在无法连接时处于挂起状态。通常建议超时设置在 30 秒以内。

<span><span><span class="hljs-variable">$timeout</span></span><span> = </span><span><span class="hljs-number">10</span></span><span>; </span><span><span class="hljs-comment">// 设置超时为 10 秒</span></span><span>
</span></span>

3.2 错误处理

fsockopen 函数的返回值是一个资源类型（socket 连接的句柄），如果连接失败，它会返回 false。为了避免错误并对其进行处理，建议使用错误代码 $errno 和错误消息 $errstr 来进行详细记录：

<span><span><span class="hljs-keyword">if</span></span><span> (!</span><span><span class="hljs-variable">$socket</span></span><span>) {
    </span><span><span class="hljs-keyword">echo</span></span><span> </span><span><span class="hljs-string">"连接失败：<span class="hljs-subst">$errno</span></span></span><span> - </span><span><span class="hljs-subst">$errstr</span></span><span>&lt;br /&gt;\n";
    </span><span><span class="hljs-keyword">exit</span></span><span>;
}
</span></span>

3.3 数据传输模式

除了发送 HTTP 请求外，fsockopen 还可以用于发送其他协议的数据，如 FTP、SMTP、POP3 等。无论是什么协议，核心思想是通过 fwrite 发送数据，fread 或 fgets 获取响应。根据协议的不同，数据格式可能会有所变化，建议在发送数据前熟悉目标协议的请求格式。

3.4 持久连接

在某些情况下，可能希望与服务器保持长期的连接状态，这可以通过 HTTP 持久连接（Keep-Alive）来实现。通过在请求头中添加 Connection: keep-alive，你可以保持连接在多次请求之间不关闭：

<span><span><span class="hljs-variable">$request</span></span><span> = </span><span><span class="hljs-string">"GET / HTTP/1.1\r\n"</span></span><span>;
</span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"Host: <span class="hljs-subst">$host</span></span></span><span>\r\n";
</span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"Connection: keep-alive\r\n"</span></span><span>;
</span><span><span class="hljs-variable">$request</span></span><span> .= </span><span><span class="hljs-string">"\r\n"</span></span><span>;
</span></span>

3.5 使用代理服务器

有时候，你可能需要通过代理服务器与目标服务器通信。这时，可以将代理服务器的地址和端口传递给 fsockopen 来代替直接连接目标服务器：

<span><span><span class="hljs-variable">$proxy</span></span><span> = </span><span><span class="hljs-string">'proxy.example.com'</span></span><span>;
</span><span><span class="hljs-variable">$proxyPort</span></span><span> = </span><span><span class="hljs-number">8080</span></span><span>;

</span><span><span class="hljs-variable">$socket</span></span><span> = </span><span><span class="hljs-title function_ invoke__">fsockopen</span></span><span>(</span><span><span class="hljs-variable">$proxy</span></span><span>, </span><span><span class="hljs-variable">$proxyPort</span></span><span>, </span><span><span class="hljs-variable">$errno</span></span><span>, </span><span><span class="hljs-variable">$errstr</span></span><span>, </span><span><span class="hljs-variable">$timeout</span></span><span>);
</span></span>

需要注意的是，代理服务器可能需要特定的认证信息（如用户名和密码），这时需要按照代理协议的要求构建请求头。

4. 总结

fsockopen 是 PHP 中一个非常强大的函数，适用于低级网络通信。当你需要与远程服务器进行数据交换时，fsockopen 提供了一种直接且灵活的方式。掌握基本的使用方法、超时设置、错误处理以及常见协议的传输技巧，将帮助你更加高效地实现 socket 数据传输。在实际应用中，记得根据需求调整参数并确保网络请求的稳定性。