Java 为什么这段代码有时抛出UnknownHostException,但有时抛出SocketTimeoutException
Linux操作系统,Tomcat服务器,“xxx.xxxx.com”是不正确的URL 我一直在期待一个未知的后验,但有时我得到的是未知的后验。 UnknownHostException错误消息 java.net.UnknownHostException:xxx.xxxx.com位于 java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178) 位于java.net.socksocketimpl.connect(socksocketimpl.java:392) java.net.Socket.connect(Socket.java:579)位于 sun.net.NetworkClient.doConnect(NetworkClient.java:178)位于 net.www.http.HttpClient.openServer(HttpClient.java:432) SocketTimeoutException错误消息 java.net.SocketTimeoutException:连接在时超时 java.net.PlainSocketImpl.socketConnect(本机方法)位于 java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:339) 在 java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:200) 在 java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:182) 位于java.net.socksocketimpl.connect(socksocketimpl.java:392) java.net.Socket.connect(Socket.java:579)位于 sun.net.NetworkClient.doConnect(NetworkClient.java:178)位于 net.www.http.HttpClient.openServer(HttpClient.java:432)Java 为什么这段代码有时抛出UnknownHostException,但有时抛出SocketTimeoutException,java,sockets,Java,Sockets,Linux操作系统,Tomcat服务器,“xxx.xxxx.com”是不正确的URL 我一直在期待一个未知的后验,但有时我得到的是未知的后验。 UnknownHostException错误消息 java.net.UnknownHostException:xxx.xxxx.com位于 java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:178) 位于java.net.socksocketimpl.connect
只是一个猜测-有时你的应用程序可能无法连接到DNS服务器吗?这就解释了为什么你会收到SocketTimeoutException而不是UnknownHostException——你的应用程序正在尝试查找主机名,但在确定主机不存在之前超时
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);
}