Question

    URL realUrl = new URL("xxx.xxxx.com");
    URLConnection conn = realUrl.openConnection();
    conn.setRequestProperty("accept", "*/*");
    conn.setRequestProperty("connection", "Keep-Alive");
    conn.setRequestProperty("user-agent",
            "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
    conn.setDoOutput(true);
    conn.setDoInput(true);
    out = new PrintWriter(new OutputStreamWriter(conn.getOutputStream()));
    out.print(param);
    out.flush();
    in = new BufferedReader(
                    new InputStreamReader(conn.getInputStream()));
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    byte[] buf = new byte[1024];
    int len = 0;
    InputStream is = conn.getInputStream();
    while ((len = is.read(buf)) != -1) {
        System.out.println(len);
        baos.write(buf, 0, len);
    }

Linux操作系统，Tomcat服务器，＆＃34; xxx.xxxx.com＆＃34;是一个不正确的网址。

我一直在期待UnknownHostException，但有时我得到的是UnknownHostException。

UnknownHostException错误消息

java.net.UnknownHostException：xxx.xxxx.com at java.net.AbstractPlainSocketImpl.connect（AbstractPlainSocketImpl.java:178）在java.net.SocksSocketImpl.connect（SocksSocketImpl.java:392）at java.net.Socket.connect（Socket.java:579）at sun.net.NetworkClient.doConnect（NetworkClient.java:178）at sun.net.www.http.HttpClient.openServer（HttpClient.java:432）

SocketTimeoutException错误消息

java.net.SocketTimeoutException：connect time out out at java.net.PlainSocketImpl.socketConnect（Native Method）at java.net.AbstractPlainSocketImpl.doConnect（AbstractPlainSocketImpl.java:339）在 java.net.AbstractPlainSocketImpl.connectToAddress（AbstractPlainSocketImpl.java:200）在 java.net.AbstractPlainSocketImpl.connect（AbstractPlainSocketImpl.java:182）在java.net.SocksSocketImpl.connect（SocksSocketImpl.java:392）at java.net.Socket.connect（Socket.java:579）at sun.net.NetworkClient.doConnect（NetworkClient.java:178）at sun.net.www.http.HttpClient.openServer（HttpClient.java:432）

Answer 1

只是猜测 - 有时您的应用无法连接到DNS服务器吗？这可以解释为什么你收到一个SocketTimeoutException而不是一个UnknownHostException - 你的应用程序试图查找主机名但它超时才能确定主机不存在。

为什么使用此代码有时会抛出UnknownHostException，但有时会抛出SocketTimeoutException

1 个答案: