堡垒机为什么连接不上

import paramiko

def connect_to_bastion(host, port, username, password):
    try:
        client = paramiko.SSHClient()
        client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
        client.connect(hostname=host, port=port, username=username, password=password)
        print("Connected successfully!")
        client.close()
    except paramiko.AuthenticationException:
        print("Authentication failed, please verify your credentials.")
    except paramiko.SSHException as ssh_ex:
        print(f"Unable to establish SSH connection: {ssh_ex}")
    except Exception as e:
        print(f"An error occurred: {e}")

# 示例调用
connect_to_bastion('bastion.example.com', 22, 'your_username', 'your_password')