为啥 ConnectException：连接被拒绝：从 HttpURLConnection.getResponseCode() 抛出连接？ [复制]

Posted 2023-04-14

【中文标题】为啥 ConnectException：连接被拒绝：从 HttpURLConnection.getResponseCode() 抛出连接？ [复制]

【英文标题】：why ConnectException: Connection refused: connect is thrown from HttpURLConnection.getResponseCode()? [duplicate]为什么 ConnectException：连接被拒绝：从 HttpURLConnection.getResponseCode() 抛出连接？ [复制]

【发布时间】：2019-11-30 03:33:44

【问题描述】：

为什么HttpURLConnection.getResponseCode() 会抛出ConnectException: Connection refused: connect 异常？

URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.getResponseCode(); // this line

例外是：

java.net.ConnectException: Connection refused: connect
at java.net.DualStackPlainSocketImpl.connect0(Native Method)
at java.net.DualStackPlainSocketImpl.socketConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.doConnect(Unknown Source)
at java.net.AbstractPlainSocketImpl.connectToAddress(Unknown Source)
at java.net.AbstractPlainSocketImpl.connect(Unknown Source)
at java.net.PlainSocketImpl.connect(Unknown Source)
at java.net.SocksSocketImpl.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at java.net.Socket.connect(Unknown Source)
at sun.net.NetworkClient.doConnect(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.openServer(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTPHeader(Unknown Source)
at sun.net.www.http.HttpClient.parseHTTP(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(Unknown Source)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(Unknown Source)
at java.net.HttpURLConnection.getResponseCode(Unknown Source)
at com.datasoft.cbsdit.CbsditApplication.main(CbsditApplication.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:48)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:87)
at org.springframework.boot.loader.Launcher.launch(Launcher.java:50)
at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:51)

【问题讨论】：

您确定您尝试连接的远程服务器是可访问的吗？

因为该 IP:port 上没有任何东西在监听。你为什么打电话给getResponseCode()却忽略了结果？

【参考方案1】：

远程机器 URL 不正确或远程服务器已关闭， 如果您尝试使用有效的 url 值（例如：https://***.com），则上述代码可以正常工作:)