有时这是因为网点配置不好。例如:require(“dotenv”)。在你的应用程序中间件中配置没有()，或者可能是你用错误的语法写了你的端口号，比如你写了:而不是=，或者在端口号中添加了一些其他符号。

这意味着节点不能在定义的端口上侦听。将其更改为1234或2000或3000并重新启动服务器。

如果你使用的是Windows。您应该重新启动Windows NAT Driver服务。

以管理员身份打开命令提示符并运行

net stop winnat

then

net start winnat

就是这样。

这是因为我安装了Nord VPN，它是自动盯着窗口。

这对我来说工作得很好，用这个代码将你的端口设置在页面底部

     let port = process.env.PORT;
if (port == null || port == "") {
    port = 3000;
}

app.listen(port, function() {
    console.log('app started successfully')
});

我尝试了上面给出的每个答案，但没有任何工作，然后我发现我忘记在.env文件中声明变量之前添加const。

之前:

PORT = 5000;
HOST = "127.0.0.1";

后:

const PORT = 5000;
const HOST = "127.0.0.1";

查看这个参考链接:

Give Safe User Permission To Use Port 80 Remember, we do NOT want to run your applications as the root user, but there is a hitch: your safe user does not have permission to use the default HTTP port (80). You goal is to be able to publish a website that visitors can use by navigating to an easy to use URL like http://ip:port/ Unfortunately, unless you sign on as root, you’ll normally have to use a URL like http://ip:port - where port number > 1024. A lot of people get stuck here, but the solution is easy. There a few options but this is the one I like. Type the following commands: sudo apt-get install libcap2-bin sudo setcap cap_net_bind_service=+ep `readlink -f \`which node\`` Now, when you tell a Node application that you want it to run on port 80, it will not complain.