java.net.SocketException: No buffer space available (maximum connections reached?): connect

        最近，有项目反馈调用第三方接口失败，查不到数据。现场用soapUI工具试了下，点执行按钮，一闪而过，接口没有任何返回值。一开始以为是第三方服务问题，后来查看日志，发现是自己的问题，报错如下：

Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): 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 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.(Unknown Source)
	at sun.net.www.http.HttpClient.New(Unknown Source)
	at sun.net.www.http.HttpClient.New(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.plainConnect(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.connect(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.getOutputStream0(Unknown Source)
	at sun.net.www.protocol.http.HttpURLConnection.getOutputStream(Unknown Source)
	at org.apache.cxf.transport.http.URLConnectionHTTPConduit$URLConnectionWrappedOutputStream.setupWrappedStream(URLConnectionHTTPConduit.java:274)
	at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.handleHeadersTrustCaching(HTTPConduit.java:1343)
	at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.onFirstWrite(HTTPConduit.java:1304)
	at org.apache.cxf.transport.http.URLConnectionHTTPConduit$URLConnectionWrappedOutputStream.onFirstWrite(URLConnectionHTTPConduit.java:307)
	at org.apache.cxf.io.AbstractWrappedOutputStream.write(AbstractWrappedOutputStream.java:47)
	at org.apache.cxf.io.AbstractThresholdOutputStream.write(AbstractThresholdOutputStream.java:69)
	at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.close(HTTPConduit.java:1356)
	... 116 common frames omitted

        Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect，看样子是连接数太多，耗尽了某种资源。

        执行命令：netstat -ano （windows下查看当前所有的连接），发现大量的TCP连接，如图：

         打开任务管理器，查看PID为60204的进程，发现是个Java进程，如图：

        然后，逐一排查，发现有个Java应用，由于配置的xxljob服务地址不正确，连接失败又不断重试，如图：

         上述问题导致TCP连接过多，资源耗尽，其他Java应用无法建立TCP连接，接口调用自然报错。找到问题了，关掉有问题的Java应用，配置正确的xxljob服务地址，重启，问题解决。