我试图从运行.net应用程序的Docker容器访问服务器上的PostgreSQL。我的Dockerfile包含以下环境变量：

ENV DB_DATABASE=db_name
ENV DB_USERNAME=db_username
ENV DB_PASSWORD=db_pw
ENV DB_HOST=public IP (not localhost!)
ENV DB_PORT=port (not the standard 5432)

在Startup.cs中，我这样构造连接字符串：

string host =  Environment.GetEnvironmentVariable("DB_HOST").ToString();
string port =  Environment.GetEnvironmentVariable("DB_PORT").ToString();
string db_name = Environment.GetEnvironmentVariable("DB_DATABASE").ToString();
string db_username = Environment.GetEnvironmentVariable("DB_USERNAME").ToString();
string db_password = Environment.GetEnvironmentVariable("DB_PASSWORD").ToString();

string db_setting = String.Format("Host={0}; Port={1}; Username={2}; Password={3}; Database={4};",host, port, db_username, db_password, db_name);

我确信数据库的端口，IP等没有错误，因为它们在其他Docker容器中使用。我得到的错误：

System.InvalidOperationException: An exception has been raised that is likely due to a transient failure.
       ---> Npgsql.NpgsqlException (0x80004005): Exception while connecting
       ---> System.Net.Sockets.SocketException (111): Connection refused

他们的文件错误点我是数据库查询。