GCP Tomcat java.net.ConnectException:拒绝连接（拒绝连接）

情况： 当从ReactJS/nginx调用restapi时，会出现此问题。然后Java/Tomcat对Python/Flask服务器进行另一个RESTAPI调用。来自Flask的响应由Tomcat发送到ReactJS

Call flow:
Receive REST API call from ReactJS to Java/Tomcat (){
  response = send REST API from Java/Tomcat to python/Flask();
  return response;
}

Rest API运行时发生以下错误(http://localhost:5000/adb/killserver/1234)从基于GCP VM的Java客户端代码发送到基于python flask的服务器

java.net.ConnectException: Connection refused (Connection refused)
    at java.net.PlainSocketImpl.socketConnect(Native Method)
    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.SocksSocketImpl.connect(SocksSocketImpl.java:392)
    at java.net.Socket.connect(Socket.java:607)
    at java.net.Socket.connect(Socket.java:556)
    at sun.net.NetworkClient.doConnect(NetworkClient.java:180)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
    at sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
    at sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
    at sun.net.www.http.HttpClient.New(HttpClient.java:339)
    at sun.net.www.http.HttpClient.New(HttpClient.java:357)
    at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1226)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
    at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
    at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:990)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1570)
    at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
    at java.net.HttpURLConnection.getResponseCode(HttpURLConnection.java:480)
    at com.example.APKGeneration.restapi.MyGETRequest(restapi.java:35)
    at com.example.APKGeneration.APKGeneration.sendGetMessage(APKGeneration.java:423)
    at com.example.APKGeneration.APKGeneration.killADBRest(APKGeneration.java:433)
    at com.example.APKGeneration.APKGeneration.executeTestcases(APKGeneration.java:113)
    at com.example.Common.design.onClickBtnTestExecutionState(design.java:523)
    at com.digitran.vte.MyResource.ExecuteTestsAndSaveInMongoDB(MyResource.java:1062)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:151)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:171)
    at org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$ResponseOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:152)
    at org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:104)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:387)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:331)
    at org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:103)
    at org.glassfish.jersey.server.ServerRuntime$1.run(ServerRuntime.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    at org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    at org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:297)
    at org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:254)
    at org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1030)
    at org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:373)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:381)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:344)
    at org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:221)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at com.digitran.filters.CorsFilter.doFilter(CorsFilter.java:27)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
    at psiprobe.Tomcat90AgentValve.invoke(Tomcat90AgentValve.java:35)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:374)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:748)

python flask代码如下所示：

public static StringBuffer MyGETRequest(String getUrlString) throws IOException {
        URL urlForGetRequest = new URL(getUrlString);
        StringBuffer response = new StringBuffer();
        String readLine = null;
        HttpURLConnection conection = (HttpURLConnection) urlForGetRequest.openConnection();
        conection.setRequestMethod("GET");
        int responseCode = conection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) {
            BufferedReader in = new BufferedReader(
                new InputStreamReader(conection.getInputStream()));         
            while ((readLine = in .readLine()) != null) {
                response.append(readLine);
            } in .close();
            // print result
            System.out.println("JSON String Result " + response.toString());
            //GetAndPost.POSTRequest(response.toString());
        } else {
            System.out.println("GET NOT WORKED");
        }
        return response;
    }

@app.route('/adb/killserver/<uuid>', methods=['GET', 'POST'])
def adbkillserver(uuid):
    print("You are getting adb kill-server request")
    command = "adb kill-server"
    result = run_command(command)
    print("result = ",result)
    return "adb kill server called"

@app.route（'/adb/killserver/'，方法=['GET'，'POST']）
def adbkillserver（uuid）：
打印（“您收到adb kill服务器请求”）
command=“adb kill server”
结果=运行命令（命令）
打印（“result=，result”）
返回“adb kill server called”

当与WSL、Tomcat和War环境一起部署时，Java和Python代码都可以正常工作

但在GCP、Tomcat和战争环境中部署时不起作用

在GCP中，为端口8080（Java）和5000（python）打开防火墙

问题:

此错误是否与GCP防火墙设置有关

此错误是否与CORS有关

为什么它在WSL环境中工作？但不在GCP中

请提供此问题的解决方案

---

我不熟悉GCP，但您确定Java和Python进程都在同一台主机上运行吗？因为您调用了localhost.ReactJS/nginx上的Python端点，所以询问是在GCP 1st VM上运行的。Java/Tomcat正在GCP2nd虚拟机上运行。Python/Flask正在localhost上运行。域“localhost”不会解析为全局唯一的主机，例如“google.com”。相反，如果要将网络客户端连接到与客户端部署在同一主机上的某个网络资源，可以将客户端配置为使用localhost。因此，我假设，在第一个场景中，所有三个服务都在同一台机器上运行（您的开发机器？），然后在非工作场景中，三个服务分布在不同的机器上。因此，如果您将Tomcat配置为连接到localhost:5000，它将在GCP2nd VM上查找该服务。谢谢。这是有道理的。我尝试使用我电脑的ip地址，但没有成功。字符串getUrlString=“”；您的电脑不是直接连接到internet，而是连接到网络路由器，而网络路由器又是internet的网关。使用像whatismyip.com这样的服务来查找路由器的当前IP（您的提供商通常不分配固定IP，因此请做好准备，它将每天更改。）一些路由器提供端口转发，因此原则上您可以向internet公开Flask/Python服务。但是，请注意，这可能会带来严重的安全问题。为什么不考虑将烧瓶/ Python服务部署到第三GCP VM？