secket 的几种构造方法

	Socket()           Creates an unconnected socket, with the system-default type of SocketImpl.
	Socket(InetAddress address, int port)           Creates a stream socket and connects it to the specified port number at the specified IP address.
	Socket(InetAddress host, int port, boolean stream)           Deprecated. Use DatagramSocket instead for UDP transport.
	Socket(InetAddress address, int port, InetAddress localAddr, int localPort)           Creates a socket and connects it to the specified remote address on the specified remote port.
	Socket(Proxy proxy)           Creates an unconnected socket, specifying the type of proxy, if any, that should be used regardless of any other settings.
protected	Socket(SocketImpl impl)           Creates an unconnected Socket with a user-specified SocketImpl.
	Socket(String host, int port)           Creates a stream socket and connects it to the specified port number on the named host.
	Socket(String host, int port, boolean stream)           Deprecated. Use DatagramSocket instead for UDP transport.
	Socket(String host, int port, InetAddress localAddr, int localPort)           Creates a socket and connects it to the specified remote host on the specified remote port.

客户端连接服务器可能出现的异常

UnKnowHostException 无法识别主机或者ip地址
ConnectException 拒绝连接
sockettimeoutException 连接超时
bindException 无法绑定端口