打开的插座和连接的插座有什么区别？ [英] Whats the difference between a socket which is open and a socket which is connected?

问题描述

Java Socket 类有两种方法 isClosed 和 isConnected 分别检查插座是否已关闭或已连接。我想知道一个只打开的TCP套接字和一个打开并连接的TCP套接字有什么区别，这与UDP有什么区别。

The Java Socket class has two methods isClosed and isConnected to check whether the socket is closed or connected respectively. I wanted to know what's the difference between a TCP socket which is only open and a TCP socket which is open and connected, and how is this different from UDP.

推荐答案

简单地说， open 的 Socket 是一个等待连接或成功的套接字连接另一个 Socket 。当套接字关闭时，意味着此套接字不再可用于连接，并且它的资源已经被释放。连接的 Socket ，这意味着套接字连接到另一个 Socket 。

To put things simply, a Socket that is open is a socket that is either waiting for connection or has successfully connected with another Socket. When a socket has been closed, it means that this socket is no longer available for connection, and that it's resources has already been released. A Socket that is connected, well, it means that the socket is connected to another Socket.

所以套接字可以..

• 同时打开并连接。


• 打开并且没有同时连接。


• 没有连接关闭时。

更新

来自@Bryan

显然，TCP套接字有半封闭或半开状态;哪个用法（今天）与其原始含义不同。有关此链接的更多信息。

Apparently, there are half-closed or half-open states for TCP Sockets; which usage (today) is different from its original meaning. More on this link.

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