java - Windows平台上socket连接异常为什么会有差异

Question

在 Windows 平台上，我运行这段代码:

代码:

Socket socket = new Socket();
    try {
        socket.connect(new InetSocketAddress("127.0.0.1", 8080), 500);
    } catch (Exception e) {
        e.printStackTrace();
    }
    socket = new Socket();
    socket.connect(new InetSocketAddress("127.0.0.1", 8080), 1100);

127.0.0.1:8080 无法访问，但我得到了不同的异常:

java.net.SocketTimeoutException: connect timed out
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.hash.test.TestRxJava.main(TestRxJava.java:14)
Exception in thread "main" java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at    java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.hash.test.TestRxJava.main(TestRxJava.java:19)

可以看到，一个是SocketTimeoutException，一个是ConnectException；

我很困惑为什么异常是不同的，这个异常导致我正在使用的框架出现一些问题(Spring Ribbon，相关问题是:ribbon issue)

希望有人能解释一下:

1. 为什么异常不同

2. 我什么时候会得到“SocketTimeoutException:连接超时”，我什么时候会得到另一个？

非常感谢

---

@乔纳森·罗森

我翻了一下代码，结果一样:

Socket socket = new Socket();
    try {
        socket.connect(new InetSocketAddress("127.0.0.1", 8080), 1100);
    } catch (Exception e) {
        e.printStackTrace();
    }
    socket = new Socket();
    socket.connect(new InetSocketAddress("127.0.0.1", 8080), 500);

结果:

java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.transsnet.afbet.factsCenter.sdk.SDKTest.main(SDKTest.java:726)
Exception in thread "main" java.net.SocketTimeoutException: connect timed out
at java.net.DualStackPlainSocketImpl.waitForConnect(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(DualStackPlainSocketImpl.java:85)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:172)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at com.transsnet.afbet.factsCenter.sdk.SDKTest.main(SDKTest.java:731)

Answer 1

因为您指定了不同的连接超时。 500 毫秒对于实际的连接超时来说太短了，但是，由于您指定了它，并且在该超时期限内连接没有成功，所以您得到的是连接超时，这是可以预料的。当您指定一个更现实的(只是)超时 1100 毫秒时，您遇到了潜在的问题，即连接拒绝，因为没有任何东西在目标 IP:port 上监听。

请注意，这段代码中存在套接字泄漏。