In a broad sense, Socket - is just that, a socket, just like your electrical, cable or telephone socket. A point where "requisite stuff" (power, signal, information) can go out and come in from. It hides a lot of detailed stuff, which is not required for the use of the "requisite stuff". In software parlance, it provides a generic way of defining a mechanism of communication between two entities (those entities could be anything - two applications, two physically separate devices, User & Kernel space within an OS, etc)

端口是端点标识符。它区分一个端点和另一个端点。在网络级别，它将一个应用程序与另一个应用程序区分开来，以便网络堆栈可以将信息传递给适当的应用程序。

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。

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.

套接字地址是一个IP地址和端口号

123.132.213.231         # IP address
               :1234    # port number
123.132.213.231:1234    # socket address

当两个套接字绑定在一起时，就发生了连接。

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。

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.