套接字基本上是网络通信的端点，至少由一个ip地址和一个端口组成。在Java/ c#中，套接字是双向连接一侧的高级实现。

还有Java教程中的一个(非规范的)定义。

从Oracle Java教程:

套接字是网络上运行的两个程序之间双向通信链路的一个端点。套接字与端口号绑定，以便TCP层可以识别数据要发送到的应用程序。

A socket is a communication endpoint. A socket is not directly related to the TCP/IP protocol family, it can be used with any protocol your system supports. The C socket API expects you to first get a blank socket object from the system that you can then either bind to a local socket address (to directly retrieve incoming traffic for connection-less protocols or to accept incoming connection requests for connection-oriented protocols) or that you can connect to a remote socket address (for either kind of protocol). You can even do both if you want to control both, the local socket address a socket is bound to and the remote socket address a socket is connected to. For connection-less protocols connecting a socket is even optional but if you don't do that, you'll have to also pass the destination address with every packet you want to send over the socket as how else would the socket know where to send this data to? Advantage is that you can use a single socket to send packets to different socket addresses. Once you have your socket configured and maybe even connected, consider it to be a bi-directional communication pipe. You can use it to pass data to some destination and some destination can use it to pass data back to you. What you write to a socket is send out and what has been received is available for reading.

Ports on the other hand are something that only certain protocols of the TCP/IP protocol stack have. TCP and UDP packets have ports. A port is just a simple number. The combination of source port and destination port identify a communication channel between two hosts. E.g. you may have a server that shall be both, a simple HTTP server and a simple FTP server. If now a packet arrives for the address of that server, how would it know if that is a packet for the HTTP or the FTP server? Well, it will know so as the HTTP server will run on port 80 and the FTP server on port 21, so if the packet arrives with a destination port 80, it is for the HTTP server and not for the FTP server. Also the packet has a source port since without such a source port, a server could only have one connection to one IP address at a time. The source port makes it possible for a server to distinguish otherwise identical connections: they all have the same destination port, e.g. port 80, the same destination IP (the IP of the server), and the same source IP, as they all come from the same client, but as they have different source ports, the server can distinguish them from each other. And when the server sends back replies, it will do so to the port the request came from, that way the client can also distinguish different replies it receives from the same server.

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。

套接字基本上是网络通信的端点，至少由一个ip地址和一个端口组成。在Java/ c#中，套接字是双向连接一侧的高级实现。

还有Java教程中的一个(非规范的)定义。