SpringBoot Netty Web Server will not start if using Unix Domain Sockets

Spring Boot version: 2.4.1

I am trying to custmoize Spring Boot HttpServer to use unix domain socket instead of http port using

@Configuration
public class NettyConfig {

    @Bean
    public NettyReactiveWebServerFactory factory() {
        NettyReactiveWebServerFactory factory = new NettyReactiveWebServerFactory();
        factory.setServerCustomizers(Collections.singletonList(new NettyServerCustomizer() {

            @Override
            public HttpServer apply(HttpServer httpServer) {
                return httpServer.bindAddress(() -> new DomainSocketAddress("/tmp/test.sock"));
            }

        }));
        return factory;
    }
}

Error comes while NettyWebServer is trying to log port, see NettWebServer.java:109

logger.info("Netty started on port(s): " + getPort());

Linked stackoverflow question - https://stackoverflow.com/questions/65319068/unix-domain-socket-configuration-in-spring-boot-webflux

Code to reproduce the issue - uds.zip

Comment From: philwebb

Copying the stacktrace from stackoverflow.com:

13:05:36.706 ERROR [restartedMain] SpringApplication.reportFailure:856 :    Application run failed
org.springframework.context.ApplicationContextException: Failed to start bean 'webServerStartStop'; nested exception is java.lang.UnsupportedOperationException
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:181)
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54)
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356)
    at java.base/java.lang.Iterable.forEach(Iterable.java:75)
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155)
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123)
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:942)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:591)
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:63)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298)
    at com.avis.biverve.EntryPoint.main(EntryPoint.java:25)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49)
Caused by: java.lang.UnsupportedOperationException
    at reactor.netty.DisposableServer.port(DisposableServer.java:69)
    at org.springframework.boot.web.embedded.netty.NettyWebServer.getPort(NettyWebServer.java:193)
    at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:109)
    at org.springframework.boot.web.reactive.context.WebServerManager.start(WebServerManager.java:54)
    at org.springframework.boot.web.reactive.context.WebServerStartStopLifecycle.start(WebServerStartStopLifecycle.java:40)
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178)
    ... 20 more

Comment From: philwebb

Looks like https://github.com/reactor/reactor-netty/commit/4346464a45c12b440ed8b6728653aba85293e7dd changed the method.

Comment From: philwebb

Thanks for the detailed report and the sample. I've pushed a fix for 2.4.2.

Comment From: philwebb

I spoke too soon. The sample fails with

org.springframework.boot.web.server.PortInUseException: Port -1 is already in use
    at org.springframework.boot.web.embedded.netty.NettyWebServer.lambda$start$2(NettyWebServer.java:105) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.server.PortInUseException.ifCausedBy(PortInUseException.java:103) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:103) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.reactive.context.WebServerManager.start(WebServerManager.java:54) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.reactive.context.WebServerStartStopLifecycle.start(WebServerStartStopLifecycle.java:40) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.2.jar!/:5.3.2]
    at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:940) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:591) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:63) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at com.avis.uds.UdsApplication.main(UdsApplication.java:10) ~[classes!/:0.0.1-SNAPSHOT]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:107) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
Caused by: reactor.netty.ChannelBindException: Failed to bind on [/tmp/test.sock]
    Suppressed: java.lang.Exception: #block terminated with an error
        at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:139) ~[reactor-core-3.4.1.jar!/:3.4.1]
        at reactor.core.publisher.Mono.block(Mono.java:1727) ~[reactor-core-3.4.1.jar!/:3.4.1]
        at reactor.netty.transport.ServerTransport.bindNow(ServerTransport.java:145) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
        at reactor.netty.transport.ServerTransport.bindNow(ServerTransport.java:130) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
        at org.springframework.boot.web.embedded.netty.NettyWebServer.startHttpServer(NettyWebServer.java:145) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:100) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.web.reactive.context.WebServerManager.start(WebServerManager.java:54) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.web.reactive.context.WebServerStartStopLifecycle.start(WebServerStartStopLifecycle.java:40) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.2.jar!/:5.3.2]
        at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
        at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:940) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:591) ~[spring-context-5.3.2.jar!/:5.3.2]
        at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:63) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
        at com.avis.uds.UdsApplication.main(UdsApplication.java:10) ~[classes!/:0.0.1-SNAPSHOT]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
        at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
        at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:107) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.Launcher.launch(Launcher.java:58) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
        at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
Caused by: java.lang.IllegalArgumentException: Unsupported channel type: ServerDomainSocketChannel
    at reactor.netty.resources.DefaultLoopNIO.getChannel(DefaultLoopNIO.java:50) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.resources.LoopResources.onChannel(LoopResources.java:214) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.tcp.TcpResources.onChannel(TcpResources.java:208) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.transport.TransportConfig.lambda$connectionFactory$0(TransportConfig.java:265) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.transport.TransportConnector.doInitAndRegister(TransportConnector.java:171) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.transport.TransportConnector.bind(TransportConnector.java:77) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.transport.ServerTransport.lambda$bind$0(ServerTransport.java:111) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.core.publisher.MonoCreate.subscribe(MonoCreate.java:57) ~[reactor-core-3.4.1.jar!/:3.4.1]
    at reactor.core.publisher.Mono.subscribe(Mono.java:4046) ~[reactor-core-3.4.1.jar!/:3.4.1]
    at reactor.core.publisher.Mono.block(Mono.java:1726) ~[reactor-core-3.4.1.jar!/:3.4.1]
    at reactor.netty.transport.ServerTransport.bindNow(ServerTransport.java:145) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at reactor.netty.transport.ServerTransport.bindNow(ServerTransport.java:130) ~[reactor-netty-core-1.0.2.jar!/:1.0.2]
    at org.springframework.boot.web.embedded.netty.NettyWebServer.startHttpServer(NettyWebServer.java:145) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.embedded.netty.NettyWebServer.start(NettyWebServer.java:100) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.reactive.context.WebServerManager.start(WebServerManager.java:54) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.web.reactive.context.WebServerStartStopLifecycle.start(WebServerStartStopLifecycle.java:40) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.2.jar!/:5.3.2]
    at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
    at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:940) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:591) ~[spring-context-5.3.2.jar!/:5.3.2]
    at org.springframework.boot.web.reactive.context.ReactiveWebServerApplicationContext.refresh(ReactiveWebServerApplicationContext.java:63) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:767) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:759) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:426) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:326) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-2.4.2-SNAPSHOT.jar!/:2.4.2-SNAPSHOT]
    at com.avis.uds.UdsApplication.main(UdsApplication.java:10) ~[classes!/:0.0.1-SNAPSHOT]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
    at java.base/java.lang.reflect.Method.invoke(Method.java:566) ~[na:na]
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:107) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]
    at org.springframework.boot.loader.JarLauncher.main(JarLauncher.java:88) ~[uds-0.0.1-SNAPSHOT.jar:0.0.1-SNAPSHOT]

Comment From: philwebb

I'd like to fix that misleading PortInUseException, but adding the following to the sample fixes the issue:

<dependency>
      <groupId>io.netty</groupId>
      <artifactId>netty-transport-native-kqueue</artifactId>
      <version>${netty.version}</version>
      <classifier>osx-x86_64</classifier>
</dependency>

Comment From: anupam-contaque

For a local quick fix, I changed NettyWebServer#getPort to

public int getPort() {
    if (this.disposableServer != null) {
        try {
            return this.disposableServer.port();
        }
        catch (UnsupportedOperationException ex) {
            return 0;
        }
    }
    return 0;
}

and added a Controller to the sample

@RestController
public class DemoController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello world";
    }
}

but when I try to test the sample with curl as

curl -GET --unix-socket /tmp/test.sock http://localhost/hello/

I get following error

java.lang.NullPointerException: null
    at reactor.netty.http.server.HttpServerOperations.scheme(HttpServerOperations.java:373) ~[reactor-netty-http-1.0.2.jar:1.0.2]
    at org.springframework.http.server.reactive.ReactorServerHttpRequest.getScheme(ReactorServerHttpRequest.java:106) ~[spring-web-5.3.2.jar:5.3.2]
    at org.springframework.http.server.reactive.ReactorServerHttpRequest.resolveBaseUrl(ReactorServerHttpRequest.java:74) ~[spring-web-5.3.2.jar:5.3.2]
    at org.springframework.http.server.reactive.ReactorServerHttpRequest.initUri(ReactorServerHttpRequest.java:70) ~[spring-web-5.3.2.jar:5.3.2]
    at org.springframework.http.server.reactive.ReactorServerHttpRequest.<init>(ReactorServerHttpRequest.java:62) ~[spring-web-5.3.2.jar:5.3.2]
    at org.springframework.http.server.reactive.ReactorHttpHandlerAdapter.apply(ReactorHttpHandlerAdapter.java:58) ~[spring-web-5.3.2.jar:5.3.2]
    at org.springframework.http.server.reactive.ReactorHttpHandlerAdapter.apply(ReactorHttpHandlerAdapter.java:40) ~[spring-web-5.3.2.jar:5.3.2]
    at reactor.netty.http.server.HttpServer$HttpServerHandle.onStateChange(HttpServer.java:628) ~[reactor-netty-http-1.0.2.jar:1.0.2]
    at reactor.netty.ReactorNetty$CompositeConnectionObserver.onStateChange(ReactorNetty.java:612) ~[reactor-netty-core-1.0.2.jar:1.0.2]
    at reactor.netty.transport.ServerTransport$ChildObserver.onStateChange(ServerTransport.java:453) ~[reactor-netty-core-1.0.2.jar:1.0.2]
    at reactor.netty.http.server.HttpServerOperations.onInboundNext(HttpServerOperations.java:510) ~[reactor-netty-http-1.0.2.jar:1.0.2]
    at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:94) ~[reactor-netty-core-1.0.2.jar:1.0.2]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at reactor.netty.http.server.HttpTrafficHandler.channelRead(HttpTrafficHandler.java:208) ~[reactor-netty-http-1.0.2.jar:1.0.2]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:436) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:324) ~[netty-codec-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:296) ~[netty-codec-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:251) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:357) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:379) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:365) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919) ~[netty-transport-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.channel.epoll.AbstractEpollStreamChannel$EpollStreamUnsafe.epollInReady(AbstractEpollStreamChannel.java:795) ~[netty-transport-native-epoll-4.1.55.Final-linux-x86_64.jar:4.1.55.Final]
    at io.netty.channel.epoll.EpollDomainSocketChannel$EpollDomainUnsafe.epollInReady(EpollDomainSocketChannel.java:138) ~[netty-transport-native-epoll-4.1.55.Final-linux-x86_64.jar:4.1.55.Final]
    at io.netty.channel.epoll.EpollEventLoop.processReady(EpollEventLoop.java:480) ~[netty-transport-native-epoll-4.1.55.Final-linux-x86_64.jar:4.1.55.Final]
    at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:378) ~[netty-transport-native-epoll-4.1.55.Final-linux-x86_64.jar:4.1.55.Final]
    at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:989) ~[netty-common-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.55.Final.jar:4.1.55.Final]
    at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) ~[netty-common-4.1.55.Final.jar:4.1.55.Final]
    at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

and curl gets empty reply from server curl: (52) Empty reply from server

Looks like ConnectionInfo is annotated with @Nullable but null is not checked to get scheme HttpServerOperations.java#L375

Comment From: violetagg

@philwebb @anupam-contaque With this fix https://github.com/reactor/reactor-netty/pull/1436 and the fix for Spring Boot proposed by @anupam-contaque

public int getPort() {
    if (this.disposableServer != null) {
        try {
            return this.disposableServer.port();
        }
        catch (UnsupportedOperationException ex) {
            return 0;
        }
    }
    return 0;
}

I was able to run the UDS example

Comment From: philwebb

Thanks @violetagg !