这个报错以后你去查看左右的机器端口占用情况，你就会发现8761端口任何服务都没有占用。所以的最大原因可能是没有覆盖SpringCloud中默认的配置。下面是SpringCloud的源码

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package org.springframework.cloud.netflix.eureka;

import com.netflix.appinfo.EurekaAccept;
import com.netflix.discovery.EurekaClientConfig;
import com.netflix.discovery.shared.transport.EurekaTransportConfig;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.NestedConfigurationProperty;
import org.springframework.core.Ordered;
import org.springframework.core.env.PropertyResolver;
import org.springframework.util.StringUtils;

@ConfigurationProperties("eureka.client")
public class EurekaClientConfigBean implements EurekaClientConfig, Ordered {
    public static final String PREFIX = "eureka.client";
    public static final String DEFAULT_URL = "http://localhost:8761/eureka/";
    public static final String DEFAULT_ZONE = "defaultZone";
    private static final int MINUTES = 60;
    @Autowired(
        required = false
    )
    PropertyResolver propertyResolver;
    private boolean enabled = true;
    @NestedConfigurationProperty
    private EurekaTransportConfig transport = new CloudEurekaTransportConfig();
    private int registryFetchIntervalSeconds = 30;
    private int instanceInfoReplicationIntervalSeconds = 30;
    private int initialInstanceInfoReplicationIntervalSeconds = 40;
    private int eurekaServiceUrlPollIntervalSeconds = 300;
    private String proxyPort;
    private String proxyHost;
    private String proxyUserName;
    private String proxyPassword;
    private int eurekaServerReadTimeoutSeconds = 8;
    private int eurekaServerConnectTimeoutSeconds = 5;
    private String backupRegistryImpl;
    private int eurekaServerTotalConnections = 200;
    private int eurekaServerTotalConnectionsPerHost = 50;
    private String eurekaServerURLContext;
    private String eurekaServerPort;
    private String eurekaServerDNSName;
    private String region = "us-east-1";
    private int eurekaConnectionIdleTimeoutSeconds = 30;
    private String registryRefreshSingleVipAddress;
    private int heartbeatExecutorThreadPoolSize = 2;
    private int heartbeatExecutorExponentialBackOffBound = 10;
    private int cacheRefreshExecutorThreadPoolSize = 2;
    private int cacheRefreshExecutorExponentialBackOffBound = 10;
    private Map<String, String> serviceUrl = new HashMap();
    private boolean gZipContent;
    private boolean useDnsForFetchingServiceUrls;
    private boolean registerWithEureka;
    private boolean preferSameZoneEureka;
    private boolean logDeltaDiff;
    private boolean disableDelta;
    private String fetchRemoteRegionsRegistry;
    private Map<String, String> availabilityZones;
    private boolean filterOnlyUpInstances;
    private boolean fetchRegistry;
    private String dollarReplacement;
    private String escapeCharReplacement;
    private boolean allowRedirects;
    private boolean onDemandUpdateStatusChange;
    private String encoderName;
    private String decoderName;
    private String clientDataAccept;
    private boolean shouldUnregisterOnShutdown;
    private boolean shouldEnforceRegistrationAtInit;
    private int order;

    public EurekaClientConfigBean() {
        this.serviceUrl.put("defaultZone", "http://localhost:8761/eureka/");
        this.gZipContent = true;
        this.useDnsForFetchingServiceUrls = false;
        this.registerWithEureka = true;
        this.preferSameZoneEureka = true;
        this.availabilityZones = new HashMap();
        this.filterOnlyUpInstances = true;
        this.fetchRegistry = true;
        this.dollarReplacement = "_-";
        this.escapeCharReplacement = "__";
        this.allowRedirects = false;
        this.onDemandUpdateStatusChange = true;
        this.clientDataAccept = EurekaAccept.full.name();
        this.shouldUnregisterOnShutdown = true;
        this.shouldEnforceRegistrationAtInit = false;
        this.order = 0;
    }

问题就是出到了 this.serviceUrl.put("defaultZone", "http://localhost:8761/eureka/");这句代码上，它给了个默认的。你要是在注册中心不配置serviceUrl的话就会出现这个问题了，所以必须配置。配置了以后会覆盖默认的。