psycopg2 连接到 postgresql 数据库 - 错误

Question

I have problem to connect to my postgreSQL database. I have databasename , password , hostname , port and I use this:

conn_string = "host='localhost' dbname='my_database' user='postgres' password='secret'"

But I got error like this:

Is the server running on host "...." and accepting TCP/IP connections on port 5432

I don't know if I used correctly host, I insert the value of hostname.
What is the difference between hostname and host? Anyone could help me?

Answer 1

psycopg2.connect(dbname=dbname, user=user, password=password, host=postgres_address, port=postgres_port)

This is working example to connect, you must define early dbname, user, password, postgres_address. If you have connection error, you can use ping for testing connection and telnet for testing openning port. Or you can use Beaver for test connection to postgres server.

Answer 2

很可能您的数据库有防火墙，请务必将您尝试连接的 IP 列入白名单。

Answer 3

Difference of host and hostname

The difference of host and hostname really depends on the context. In your context of psycopg2 and PostgreSQL connection, the host normally means the IP address of the PostgreSQL server or the resolvable name of the PostgreSQL server such as DNS name if it has. If you are running linux server, the output of command hostname is unlikely to work in your case.

psycopg2 connection

Your connection string looks OK. But I will suggest you to use below connection format:

import psycopg2
try:
    connection = psycopg2.connect(user = "sysadmin",
                                  password = "pynative@#29",
                                  host = "127.0.0.1",
                                  port = "5432",
                                  database = "postgres_db")
except (Exception, psycopg2.Error) as error :
    print ("Error while connecting to PostgreSQL", error)

You should use the IP address as the host value.

Troubleshooting

In the case of connection error, you should use other tools to test the connection of PostgreSQL server such as psql , pgAdmin4 or DBeaver .

You can also use telnet or netcat tools to test the network connection of PostgreSQL server, such as

telnet PostgreSQL_ip_address 5432

nc -v PostgreSQL_ip_address 5432