这个问题已经有了理论上的答案。我想举一个实际的例子来解释这个问题，让大家对Socket和Port有一个更清晰的理解。

我在这里找到的

This example will walk you thru the process of connecting to a website, such as Wiley. You would open your web browser (like Mozilla Firefox) and type www.wiley.com into the address bar. Your web browser uses a Domain Name System (DNS) server to look up the name www.wiley.com to identify its IP address is. For this example, the address is 192.0.2.100. Firefox makes a connection to the 192.0.2.100 address and to the port where the application layer web server is operating. Firefox knows what port to expect because it is a well-known port . The well-known port for a web server is TCP port 80. The destination socket that Firefox attempts to connect is written as socket:port, or in this example, 192.0.2.100:80. This is the server side of the connect, but the server needs to know where to send the web page you want to view in Mozilla Firefox, so you have a socket for the client side of the connection also. The client side connection is made up of your IP address, such as 192.168.1.25, and a randomly chosen dynamic port number. The socket associated with Firefox looks like 192.168.1.25:49175. Because web servers operate on TCP port 80, both of these sockets are TCP sockets, whereas if you were connecting to a server operating on a UDP port, both the server and client sockets would be UDP sockets.

单个端口可以有一个或多个连接不同外部IP的插座，如多个电源插座。

  TCP    192.168.100.2:9001     155.94.246.179:39255   ESTABLISHED     1312
  TCP    192.168.100.2:9001     171.25.193.9:61832     ESTABLISHED     1312
  TCP    192.168.100.2:9001     178.62.199.226:37912   ESTABLISHED     1312
  TCP    192.168.100.2:9001     188.193.64.150:40900   ESTABLISHED     1312
  TCP    192.168.100.2:9001     198.23.194.149:43970   ESTABLISHED     1312
  TCP    192.168.100.2:9001     198.49.73.11:38842     ESTABLISHED     1312

套接字是一种特殊类型的文件句柄，进程使用它从操作系统请求网络服务。 套接字地址是三元组: {protocol, local-address, local-process}，其中本地进程由端口号标识。

在TCP/IP套件中，例如:

{tcp, 193.44.234.3, 12345}

会话是两个进程之间的通信链接，从而描述了两者之间的关联。 关联是一个5元组，它完全指定了组成连接的两个进程: {protocol, local-address, local-process, foreign-address, foreign-process}

在TCP/IP套件中，例如:

{tcp, 193.44.234.3, 1500, 193.44.234.5, 21}

可能是一个有效的关联。

半关联是: {protocol, local-address, local-process}

or

{protocol, foreign-address, foreign-process}

它们指定连接的每一半。

半关联也称为套接字或传输地址。也就是说，套接字是可以在网络中命名和寻址的通信端点。 套接字接口是通信协议的几个应用程序编程接口(api)之一。它被设计为一个通用的通信编程接口，最初由4.2BSD UNIX系统引入。虽然还没有标准化，但已经成为事实上的行业标准。

这些是基本的网络概念，所以我将以一种简单而全面的方式详细解释它们。

插座就像电话(即端到端通信设备) IP就像你的电话号码(即你的插座地址) 端口就像您想要与之交谈的人(即您想从该地址订购的服务) 插座可以是客户端也可以是服务器端(例如，在公司中，客户支持的电话是服务器，但你家里的电话主要是客户端)

因此，网络中的套接字是绑定到一对(ip，端口)=(地址，服务)的虚拟通信设备。

注意:

A machine, a computer, a host, a mobile, or a PC can have multiple addresses , multiple open ports, and thus multiple sockets. Like in an office you can have multiple telephones with multiple telephone numbers and multiple people to talk to. Existence of an open/active port necessitate that you must have a socket bound to it, because it is the socket that makes the port accessible. However, you may have unused ports for the time being. Also note, in a server socket you can bind it to (a port, a specific address of a machine) or to (a port, all addresses of a machine) as in the telephone you may connect many telephone lines (telephone numbers) to a telephone or one specific telephone line to a telephone and still you can reach a person through all these telephone lines or through a specific telephone line. You can not associate (bind) a socket with two ports as in the telephone usually you can not always have two people using the same telephone at the same time . Advanced: on the same machine you cannot have two sockets with same type (client, or server) and same port and ip. However, if you are a client you can open two connections, with two sockets, to a server because the local port in each of these client's sockets is different)

希望它能消除你的疑虑

一个连接套接字(fd)用于本地地址+本地端口+对端地址+对端端口。通过套接字抽象处理recv/发送数据。 一个监听套接字(fd)用于本地地址+本地监听端口。进程可以通过套接字接受新的连接。

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