Server Testing Guide - theLAB Wiki

🎯

Overview

This guide covers essential techniques for testing your own servers using two powerful command-line tools:

Tools Covered

🔧 netcat (nc)

Swiss army knife for network connections - excellent for basic connectivity tests and data transfer

🚀 hping3

Advanced packet crafting and network testing tool for sophisticated testing scenarios

⚠️ Important Safety Notice

Always test only servers you own or have explicit permission to test. Unauthorized testing may violate terms of service or local laws.

Prerequisites

Root or sudo access on your test machine
Basic understanding of TCP/IP networking
Target servers that you own and have permission to test

📦

Installation

Ubuntu/Debian

sudo apt-get update
sudo apt-get install netcat-openbsd hping3

CentOS/RHEL/Fedora

sudo yum install nc hping3
# or for newer versions:
sudo dnf install nc hping3

macOS

# netcat is pre-installed
brew install hping

🔌

Netcat (nc) Testing

Basic Port Connectivity Testing

Test if a port is open

# Basic TCP connection test
nc -zv server_ip port
nc -zv 192.168.1.100 80

# Test multiple ports
nc -zv 192.168.1.100 80-90

# UDP port test
nc -zuv 192.168.1.100 53

Test port ranges

# Scan ports 1-1000
nc -zv server_ip 1-1000

# Common service ports
nc -zv server_ip 21,22,23,25,53,80,110,143,443,993,995

Service Banner Grabbing

HTTP service testing

# Connect to HTTP server
nc server_ip 80
# Then type: GET / HTTP/1.1 followed by two newlines

# Automated HTTP test
echo -e "GET / HTTP/1.1\r\nHost: server_ip\r\n\r\n" | nc server_ip 80

SSH banner grab

nc server_ip 22
# Server will respond with SSH version banner

File Transfer Testing

Simple file server

# On receiving server
nc -l -p 8080 > received_file.txt

# On sending machine
nc server_ip 8080 < file_to_send.txt

⚡

hping3 Advanced Testing

Basic Connectivity Tests

ICMP ping alternative

# Standard hping3 ping
hping3 -c 4 server_ip

# TCP ping to specific port
hping3 -S -p 80 -c 4 server_ip

# UDP ping
hping3 -2 -p 53 -c 4 server_ip

Firewall and Filter Testing

Test firewall rules

# Test if TCP port is filtered
hping3 -S -p 443 -c 3 server_ip

# Test different TCP flags
hping3 -F -p 80 -c 3 server_ip  # FIN flag
hping3 -A -p 80 -c 3 server_ip  # ACK flag
hping3 -P -p 80 -c 3 server_ip  # PUSH flag

Load Testing

🔔 Controlled Testing

Be extremely careful with flood tests. Start with low rates and monitor your server's response.

Connection rate testing

# Controlled rate SYN test
hping3 -S -p 80 -i u1000 server_ip  # 1000 microsecond interval

# Test connection establishment rate
hping3 -S -p 80 -i u100 -c 1000 server_ip

🎬

Comprehensive Testing Scenarios

Web Server Testing

# 1. Basic connectivity
nc -zv web_server 80 443

# 2. HTTP response test
echo -e "GET / HTTP/1.1\r\nHost: web_server\r\n\r\n" | nc web_server 80

# 3. SSL/TLS port test
nc -zv web_server 443

# 4. Load response test
hping3 -S -p 80 -i u1000 -c 100 web_server

Database Server Testing

# MySQL/MariaDB
nc -zv db_server 3306

# PostgreSQL
nc -zv db_server 5432

# Redis
nc -zv db_server 6379
echo "PING" | nc db_server 6379

# MongoDB
nc -zv db_server 27017

SSH Server Testing

# Basic connectivity
nc -zv ssh_server 22

# Banner grab
nc ssh_server 22

# Test SSH with different algorithms
hping3 -S -p 22 -c 3 ssh_server

📊

Performance Benchmarking

Bandwidth Testing

Simple bandwidth test using nc

# Server side:
nc -l -p 8080 | pv > /dev/null

# Client side:
dd if=/dev/zero bs=1M count=1000 | pv | nc server_ip 8080

Latency Testing

# Round-trip time measurement
hping3 -c 100 -i u10000 server_ip | grep round-trip

# TCP connection time
hping3 -S -p 80 -c 10 server_ip | grep round-trip

🔍

Troubleshooting Common Issues

Connection Timeouts

# Increase timeout
nc -w 10 server_ip port

# Test with different protocols
hping3 -1 server_ip  # ICMP
hping3 -2 -p 53 server_ip  # UDP
hping3 -S -p 80 server_ip  # TCP SYN

Firewall Detection

# Test for stateful firewall
hping3 -A -p 80 server_ip  # Should be dropped if stateful

# Test for port filtering
hping3 -S -p 12345 server_ip  # Test non-standard port

⭐

Best Practices

🛡️ Safety Guidelines

Always test only servers you own or have explicit permission to test
Start with gentle tests before aggressive ones
Monitor server resources during testing
Have rollback plans for any configuration changes
Document baseline performance before testing

Testing Methodology

1. Baseline establishment: Record normal server behavior

2. Incremental testing: Start with simple tests, increase complexity

3. Documentation: Keep detailed logs of all tests and results

4. Validation: Verify server functionality after each test phase

5. Cleanup: Remove any test files or temporary configurations

💡 Pro Tips

Don't test production servers during peak hours
Avoid overwhelming servers with excessive connections
Be cautious with flood tests - they can cause legitimate DoS
Always check legal compliance for your testing activities
Don't leave nc listeners running indefinitely

📋 Table of Contents