套接字 - 如何找出分配给我的端口和地址 [英] Sockets - How to find out what port and address I'm assigned

问题描述

我无法解决这个问题 - 我正在使用本指南在 C 中使用套接字 - http://binarii.com/files/papers/c_sockets.txt

I'm having trouble figuring this out - I'm working with sockets in C using this guide - http://binarii.com/files/papers/c_sockets.txt

我正在尝试使用以下方法自动获取我的 IP 和端口:

I'm trying to automatically get my ip and port using:

server.sin_port = 0;              /* bind() will choose a random port*/
server.sin_addr.s_addr = INADDR_ANY;  /* puts server's IP automatically */
...
...
bind(int fd, struct sockaddr *my_addr,int addrlen); // Bind function

绑定成功后，我如何知道我实际分配的 IP 和端口是什么?

After a successful bind, how do I find out what IP and Port I'm actually assigned?

推荐答案

如果是服务器套接字，应该调用 listen() 在您的套接字上，然后 getsockname() 找到它正在监听的端口号:

If it's a server socket, you should call listen() on your socket, and then getsockname() to find the port number on which it is listening:

struct sockaddr_in sin;
socklen_t len = sizeof(sin);
if (getsockname(sock, (struct sockaddr *)&sin, &len) == -1)
    perror("getsockname");
else
    printf("port number %d
", ntohs(sin.sin_port));

至于 IP 地址，如果您使用 INADDR_ANY 那么服务器套接字可以接受与机器的任何 IP 地址的连接，并且服务器套接字本身没有特定的 IP 地址.例如，如果您的机器有两个 IP 地址，那么您可能会在此服务器套接字上获得两个传入连接，每个连接具有不同的本地 IP 地址.您可以在套接字上使用 getsockname() 进行特定连接(从 accept() 获得)，以便找出正在使用的本地 IP 地址连接.

As for the IP address, if you use INADDR_ANY then the server socket can accept connections to any of the machine's IP addresses and the server socket itself does not have a specific IP address. For example if your machine has two IP addresses then you might get two incoming connections on this server socket, each with a different local IP address. You can use getsockname() on the socket for a specific connection (which you get from accept()) in order to find out which local IP address is being used on that connection.

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