Java ConnectException:操作超时

我有一个打开套接字连接以查询WHOIS服务器的类。不幸的是，每次我运行它（例如java WHOIS google.com），它总是抛出异常：

Contacting the WHOIS server for 'google.com' at whois.internic.net:43
Exception in thread "main" java.net.ConnectException: Operation timed out
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
    at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
    at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
    at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:432)
    at java.net.Socket.connect(Socket.java:529)
    at java.net.Socket.connect(Socket.java:478)
    at java.net.Socket.<init>(Socket.java:375)
    at java.net.Socket.<init>(Socket.java:189)
    at WHOIS.performWhoisQuery(WHOIS.java:11)
    at WHOIS.main(WHOIS.java:28)

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检查是否是防火墙问题的一种简单方法是使用

telnet

从同一台计算机连接到目标主机/端口

例如，在我的Linux设备上：

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如果您能够连接，那么问题在于您的Java程序。否则问题出在其他地方（防火墙等）。

谢谢！telnet也会随着连接超时而终止。好的，这与防火墙约束有关。我将从另一个环境中尝试它。@Birhanu Mekuria Eshete是的，但它是先连接然后超时，还是无法完全连接？它根本不连接。它以“正在尝试199.7.52.74…telnet:连接到地址199.7.52.74:操作超时telnet:无法连接到远程主机”结束

public class WHOIS {
    public static void performWhoisQuery(String host, int port, String query) throws Exception {
        System.out.println(" Contacting the WHOIS server for '" + query + "' at " + host + ":" + port);

        Socket socket = new Socket(host, port);

        InputStreamReader isr = new InputStreamReader(socket.getInputStream());
        BufferedReader br = new BufferedReader(isr);

        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        out.println(query);

        String aLine = "";
        while ((aLine = br.readLine()) != null) {
            System.out.println(aLine);
        }
    }

    public static void main(String[] args) throws Exception {
        String domainNameToCheck = args[0];
        performWhoisQuery("whois.internic.net", 43, domainNameToCheck);

    }

}

aix@aix:~$ telnet whois.internic.net 43
Trying 199.7.57.74...
Connected to whois.internic.net.
Escape character is '^]'.