在很多请求第三方服务的服务器的客户端连接中，我们看到各种超时连接的字眼，这里面总结了一下。

connectionRequestTimout

指从连接池获取连接的timeout

connetionTimeout

指客户端和服务器建立连接的timeout，
就是http请求的三个阶段，一：建立连接；二：数据传送；三，断开连接。超时后会ConnectionTimeOutException

socketTimeout

指客户端从服务器读取数据的timeout，超出后会抛出SocketTimeOutException

一言不合上源码

/** 
    * Returns the timeout in milliseconds used when requesting a connection 
    * from the connection manager. A timeout value of zero is interpreted 
    * as an infinite timeout. 
    * A timeout value of zero is interpreted as an infinite timeout. 
    * A negative value is interpreted as undefined (system default). 
    * Default: {@code -1} 
    */
   public int getConnectionRequestTimeout() {  
       return connectionRequestTimeout;  
   }  

     /** 
    * Determines the timeout in milliseconds until a connection is established. 
    * A timeout value of zero is interpreted as an infinite timeout. 
    * A timeout value of zero is interpreted as an infinite timeout. 
    * A negative value is interpreted as undefined (system default). 
    * Default: {@code -1} 
    */  
   public int getConnectTimeout() {  
       return connectTimeout;  
   }  

   /** 
    * Defines the socket timeout ({@code SO_TIMEOUT}) in milliseconds, 
    * which is the timeout for waiting for data  or, put differently, 
    * a maximum period inactivity between two consecutive data packets). 
    * A timeout value of zero is interpreted as an infinite timeout. 
    * A negative value is interpreted as undefined (system default). 
    * Default: {@code -1} 
    */  
   public int getSocketTimeout() {  
       return socketTimeout;  
   }