端口和插座可以比作银行分行。

“银行”的门牌号与IP地址类似。 银行有不同的部分，比如:

储蓄帐务部 个人贷款部 房屋贷款部 投诉部门

因此，1(储蓄账户部)、2(个人贷款部)、3(住房贷款部)和4(申诉部)是端口。

现在让我们假设你要开一个储蓄账户，你去了银行(IP地址)，然后你去了“储蓄账户部门”(端口号1)，然后你遇到了在“储蓄账户部门”工作的一名员工。让我们称他为SAVINGACCOUNT_EMPLOYEE1，用于开户。

SAVINGACCOUNT_EMPLOYEE1是套接字描述符，因此可能存在 SAVINGACCOUNT_EMPLOYEE1到SAVINGACCOUNT_EMPLOYEEN。这些都是套接字描述符。

同样地，其他部门将有员工在他们之下工作，他们类似于插座。

I know that there are lot of explanations. But, there is one more easy way to understand with practical example. We all can connect to HTTP port 80, but does it mean only one user can connect to that port at a time?. The answer is obviously 'no'. Multiple users for multiple purposes can access HTTP port 80 but they still get proper response they are waiting for, from the server, can't they?. Now think about it for a minute, how?. Yes you are correct, its IP address that uniquely identifies different users who contacts for different purposes. If you would have read the previous answers before reaching here, you would know that IP address is a part of information that socket consists. Think about it, is it possible to have a communication without sockets?. The answer is 'Yes' but you cannot run more than one application in a port but we know that we are not a 'Dump' switch that runs on just hardware.

它们是来自两个不同领域的术语:“端口”是TCP/IP网络的概念，“套接字”是API(编程)的东西。“套接字”是通过将端口和主机名或网络适配器组合成一个数据结构(可以用来发送或接收数据)而形成的(在代码中)。

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.

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.

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