端口是最简单的部分，它只是套接字的唯一标识符。套接字是进程可以用来建立连接和相互通信的东西。高个子杰夫有一个很好的电话比喻，但并不完美，所以我决定修正它:

IP和端口~电话号码 插座~电话设备 连接~电话 建立连接~拨打号码 流程，远程应用程序~人员 留言~语音

Socket is an abstraction provided by kernel to user applications for data I/O. A socket type is defined by the protocol it's handling, an IPC communication etc. So if somebody creates a TCP socket he can do manipulations like reading data to socket and writing data to it by simple methods and the lower level protocol handling like TCP conversions and forwarding packets to lower level network protocols is done by the particular socket implementation in the kernel. The advantage is that user need not worry about handling protocol specific nitigrities and should just read and write data to socket like a normal buffer. Same is true in case of IPC, user just reads and writes data to socket and kernel handles all lower level details based on the type of socket created.

端口和IP一起就像给套接字提供一个地址，虽然不是必需的，但它有助于网络通信。

端口是网络协议用来访问连接的主机的实体。端口可以是特定于应用程序的，也可以是与特定通信媒介相关的。不同的协议使用不同的端口访问主机，如HTTP使用80端口或FTP使用23端口。您可以在应用程序中分配用户定义的端口号，但这些端口号应该大于1023。

端口打开到所需主机的连接，而套接字是网络间或进程间通信的端点。 套接字是由系统通过api(应用程序编程接口)分配的。

更微妙的区别是，当系统重新启动时，端口将出现，而套接字将被销毁。

端口是最简单的部分，它只是套接字的唯一标识符。套接字是进程可以用来建立连接和相互通信的东西。高个子杰夫有一个很好的电话比喻，但并不完美，所以我决定修正它:

IP和端口~电话号码 插座~电话设备 连接~电话 建立连接~拨打号码 流程，远程应用程序~人员 留言~语音

套接字是一种数据I/O机制。端口是通信协议的契约概念。套接字可以没有端口而存在。一个端口可以没有特定的套接字而存在(例如，如果同一个端口上有几个活动的套接字，这可能是某些协议允许的)。

端口用于确定接收端应该将数据包路由到哪个套接字，在许多协议中，但它并不总是必需的，接收套接字的选择可以通过其他方式完成——端口完全是网络子系统中协议处理程序使用的工具。例如，如果协议不使用端口，数据包可以到所有侦听套接字或任何套接字。

An application consists of pair of processes which communicate over the network (client-server pair). These processes send and receive messages, into and from the network through a software interface called socket. Considering the analogy presented in the book "Computer Networking: Top Down Approach". There is a house that wants to communicate with other house. Here, house is analogous to a process, and door to a socket. Sending process assumes that there is a infrastructure on the other side of the door that will transport the data to the destination. Once the message is arrived on the other side, it passes through receiver's door (socket) into the house (process). This illustration from the same book can help you: Sockets are part of transport layer, which provides logical communication to applications. This means that from application's point of view both hosts are directly connected to each other, even though there are numerous routers and/or switches between them. Thus a socket is not a connection itself, it's the end point of the connection. Transport layer protocols are implemented only on hosts, and not on intermediate routers. Ports provide means of internal addressing to a machine. The primary purpose it to allow multiple processes to send and receive data over the network without interfering with other processes (their data). All sockets are provided with a port number. When a segment arrives to a host, the transport layer examines the destination port number of the segment. It then forwards the segment to the corresponding socket. This job of delivering the data in a transport layer segment to the correct socket is called de-multiplexing. The segment's data is then forwarded to the process attached to the socket.