HTTP Status 500 - java.net.ConnectException: Connection refused (Connection refused)

type Exception report

message java.net.ConnectException: Connection refused (Connection refused)

description The server encountered an internal error that prevented it from fulfilling this request.

exception

java.lang.RuntimeException: java.net.ConnectException: Connection refused (Connection refused)
	com.cengage.ztest.lti.LTISigningKeyResolver.loadJwkSet(LTISigningKeyResolver.java:41)
	com.cengage.ztest.lti.LTISigningKeyResolver.resolveSigningKey(LTISigningKeyResolver.java:29)
	io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:342)
	io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:513)
	io.jsonwebtoken.impl.DefaultJwtParser.parseClaimsJws(DefaultJwtParser.java:573)
	com.cengage.ztest.lti.LTIProviderServlet.verify13Request(LTIProviderServlet.java:133)
	com.cengage.ztest.lti.LTIProviderServlet.verifyRequest(LTIProviderServlet.java:104)
	com.cengage.ztest.lti.LTIProviderServlet.doPost(LTIProviderServlet.java:95)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	com.google.inject.servlet.ServletDefinition.doServiceImpl(ServletDefinition.java:290)
	com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:280)
	com.google.inject.servlet.ServletDefinition.service(ServletDefinition.java:184)
	com.google.inject.servlet.ManagedServletPipeline.service(ManagedServletPipeline.java:89)
	com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:121)
	com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:133)

root cause

java.net.ConnectException: Connection refused (Connection refused)
	java.net.PlainSocketImpl.socketConnect(Native Method)
	java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
	java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
	java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
	java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
	java.net.Socket.connect(Socket.java:607)
	sun.net.NetworkClient.doConnect(NetworkClient.java:175)
	sun.net.www.http.HttpClient.openServer(HttpClient.java:463)
	sun.net.www.http.HttpClient.openServer(HttpClient.java:558)
	sun.net.www.http.HttpClient.<init>(HttpClient.java:242)
	sun.net.www.http.HttpClient.New(HttpClient.java:339)
	sun.net.www.http.HttpClient.New(HttpClient.java:357)
	sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:1226)
	sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1162)
	sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1056)
	sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:990)
	sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1570)
	sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
	com.nimbusds.jose.util.DefaultResourceRetriever.retrieveResource(DefaultResourceRetriever.java:166)
	com.nimbusds.jose.jwk.JWKSet.load(JWKSet.java:421)
	com.nimbusds.jose.jwk.JWKSet.load(JWKSet.java:440)
	com.cengage.ztest.lti.LTISigningKeyResolver.loadJwkSet(LTISigningKeyResolver.java:39)
	com.cengage.ztest.lti.LTISigningKeyResolver.resolveSigningKey(LTISigningKeyResolver.java:29)
	io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:342)
	io.jsonwebtoken.impl.DefaultJwtParser.parse(DefaultJwtParser.java:513)
	io.jsonwebtoken.impl.DefaultJwtParser.parseClaimsJws(DefaultJwtParser.java:573)
	com.cengage.ztest.lti.LTIProviderServlet.verify13Request(LTIProviderServlet.java:133)
	com.cengage.ztest.lti.LTIProviderServlet.verifyRequest(LTIProviderServlet.java:104)
	com.cengage.ztest.lti.LTIProviderServlet.doPost(LTIProviderServlet.java:95)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	com.google.inject.servlet.ServletDefinition.doServiceImpl(ServletDefinition.java:290)
	com.google.inject.servlet.ServletDefinition.doService(ServletDefinition.java:280)
	com.google.inject.servlet.ServletDefinition.service(ServletDefinition.java:184)
	com.google.inject.servlet.ManagedServletPipeline.service(ManagedServletPipeline.java:89)
	com.google.inject.servlet.ManagedFilterPipeline.dispatch(ManagedFilterPipeline.java:121)
	com.google.inject.servlet.GuiceFilter.doFilter(GuiceFilter.java:133)

note The full stack trace of the root cause is available in the Apache Tomcat/8.5.9 logs.
Apache Tomcat/8.5.9