Java.net.SocketException:No buffer space available (maximum connections reached?): Connect problem analysis __.net

Exception Log

 caused By:java.net.SocketException:No buffer space available (maximum connections reached?): Connect at Java.net.Tw Ostacksplainsocketimpl.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) A T Java.net.PlainSocketImpl.connect (plainsocketimpl.java:172) at Java.net.SocksSocketImpl.connect ( sockssocketimpl.java:392) at Java.net.Socket.connect (socket.java:589) at Org.apache.http.conn.scheme.PlainSocketFa Ctory.connectsocket (plainsocketfactory.java:121) at Org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection (Defaultclientconnectionoperator.java : 180) at Org.apache.http.impl.conn.ManagedClientConnectionImpl.open (managedclientconnectionimpl.java:326) at ORG.A Pache.http.impl.client.DefaultRequestDirector.tryConneCT (defaultrequestdirector.java:610) at Org.apache.http.impl.client.DefaultRequestDirector.execute ( defaultrequestdirector.java:445) at Org.apache.http.impl.client.AbstractHttpClient.doExecute ( abstracthttpclient.java:835) at Org.apache.http.impl.client.CloseableHttpClient.execute (Closeablehttpclient.java : Org.apache.http.impl.client.CloseableHttpClient.execute at ORG.APACHE.HTTP.I (closeablehttpclient.java:108)
 Mpl.client.CloseableHttpClient.execute (closeablehttpclient.java:56)

Problem Analysis
Online said no buffer space available (maximum connections reached?) Because the machine port number is exhausted, TCP cannot request a new port to establish a connection. First think of to see the machine port number usage.

A large number of ports in the TIME_WAIT state, the initial estimate may be the client every time to request the server to create a TCP connection, the end of the connection, but the TCP protocol if the client actively shut down, in order to ensure that the message sent does not affect the next connection, the active shutdown needs to stay _wait State 2*MSL (Max Segment Lifetime). When the concurrent high, will produce a large number of time_wait, and in the TIME_WAIT state of the port is not immediately to establish a new connection, which leads to no buffer space available (maximum connections reached?) This exception.

Problem fixes
The troubleshooting code found that there was a rest request that created one httpclient at a time. It is equivalent to re-establish the TCP connection each time, complete 3 handshake and 4 wave.

The repaired code uses an HTTP connection pool to take a duplicate HTTP connection. This eliminates the need to create a new TCP connection every time. Not only can you avoid the port being filled up, you can also improve IO performance (TCP connection setup and shutdown are overhead). HttpClient provides Poolinghttpclientconnectionmanager classes to support the management of HTTP connection pools.