When working with PostgreSQL in a VirtualBox environment, connection issues between host and guest systems are common but solvable. The typical symptoms include:

• "Connection attempt failed" errors
• Timeout messages
• Authentication failures despite correct credentials

The VirtualBox port forwarding setup appears correct in your configuration, but let's verify the complete command syntax:

VBoxManage modifyvm "vmname" --natpf1 "pgsql,tcp,,5432,,5432"

Alternatively, you can set it through the VirtualBox GUI:

1. Right-click your VM → Settings → Network
2. Expand Advanced → Port Forwarding
3. Add rule: Name=pgsql, Protocol=TCP, Host IP=blank, Host Port=5432, Guest IP=blank, Guest Port=5432

Your pg_hba.conf needs additional considerations. Let's enhance it:

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD
host    all         all         0.0.0.0/0             md5
host    all         all         ::/0                  md5
local   all         all                              peer

Also check postgresql.conf for these critical settings:

listen_addresses = '*'
port = 5432
max_connections = 100

The network adapter type matters in VirtualBox. For PostgreSQL connectivity:

• Use NAT with port forwarding for simplest setup
• Bridged adapter for direct network access
• Host-only for secure internal networks

Run these diagnostic commands in sequence:

# On guest system:
sudo netstat -tulnp | grep 5432
sudo ufw status
ping 10.0.2.2

# On host system:
telnet localhost 5432
ping [guest-ip]

For different connection scenarios:

# Standard connection from host:
psql -h localhost -p 5432 -U username -d dbname

# Using application connection strings:
# JDBC: jdbc:postgresql://localhost:5432/dbname
# Python: psycopg2.connect(host="localhost", port=5432, user="user", password="pwd", database="db")

If problems persist, check these advanced areas:

1. Verify VirtualBox network adapter driver version
2. Test with different PostgreSQL authentication methods (trust/md5)
3. Try alternate ports to rule out conflicts
4. Examine VirtualBox logs (VBox.log in VM folder)

---

First, let's ensure your VirtualBox port forwarding is correctly set up. Run this command in your host's command prompt:

vboxmanage showvminfo "Your_VM_Name" | find "NAT"

You should see output similar to:

NIC 1 Rule(0):   name = pgsql, protocol = tcp, host ip = , host port = 5432, guest ip = , guest port = 5432

In your Ubuntu guest, examine /etc/postgresql/8.4/main/postgresql.conf:

sudo nano /etc/postgresql/8.4/main/postgresql.conf

Look for the listen_addresses parameter. It should be configured as:

listen_addresses = 'localhost,10.0.2.15'  # or your guest IP

From your Windows host, try these diagnostic commands:

telnet 127.0.0.1 5432
psql -h 127.0.0.1 -p 5432 -U postgres

Your current pg_hba.conf configuration looks good, but let's make it more robust:

# TYPE  DATABASE    USER        CIDR-ADDRESS          METHOD
host    all         all         127.0.0.1/32          md5
host    all         all         10.0.2.0/24           md5
host    all         all         192.168.1.0/24        md5

Even with firewalls disabled, try these iptables commands in your guest:

sudo iptables -A INPUT -p tcp --dport 5432 -j ACCEPT
sudo iptables -L -n | grep 5432

If port forwarding still fails, consider these alternatives:

# Bridge networking configuration in VirtualBox
VBoxManage modifyvm "Your_VM_Name" --nic1 bridged --bridgeadapter1 "Your_Network_Adapter"

# Then connect directly via guest IP:
psql -h 192.168.1.x -p 5432 -U postgres