jns

jns is a high-performance network port scanner written in Java 25 using virtual threads. It scans single hosts or entire host lists (IPv4 and IPv6) with massive concurrency and minimal resource overhead.

Features

TCP & UDP scanning — TCP everywhere, plus raw-socket UDP probing on Linux
IPv4 and IPv6 support
Service detection — optional banner recognition identifies the service behind an open port
Massive concurrency — virtual threads with configurable limits for parallel hosts, sockets, and workers per host
Flexible targets — hosts as CLI arguments, from a file, or from stdin (-i -)
Rate limiting — configurable delay between connection attempts per host
Fine-grained control — per-connection timeout, port ranges, online check toggle
Clean reporting — quiet mode, optional filtered ports, progress feedback; partial results are preserved on Ctrl-C

Requirements

Java 25 or later
Maven (for building)
Linux (only required for UDP scanning)

Build

mvn package -DskipTests

This produces target/jns-1.0-SNAPSHOT.jar.

Usage

java -jar target/jns-1.0-SNAPSHOT.jar [OPTIONS] <host>...

Examples

# Scan a single host on the default port range (1-1024)
java -jar target/jns-1.0-SNAPSHOT.jar localhost

# Scan specific ports on an IPv6 host
java -jar target/jns-1.0-SNAPSHOT.jar fd00::1 -p 22,80,443

# Scan a host list from a file
java -jar target/jns-1.0-SNAPSHOT.jar -i hosts.txt -p 1-65535

# Read hosts from stdin
cat hosts.txt | java -jar target/jns-1.0-SNAPSHOT.jar -i - -p all

# UDP scan with service detection (Linux only)
java -jar target/jns-1.0-SNAPSHOT.jar 192.168.1.5 -uu -b -p 53,123

Options

Option	Description	Default
`-p, --ports`	Ports to scan (e.g. `22,80,443` or `1-1024`)	`1-1024`
`-i, --input`	Read hosts from a file; `-` reads stdin	–
`-uu, --useUdp`	Use UDP instead of TCP (Linux only)	false
`-b, --bannerRecognition`	Recognize services from banners	false
`-t, --timeout`	Timeout in ms per connection attempt	`3000`
`-d, --delay`	Delay in ms between connection attempts per host	`0`
`-hl, --hostsLimit`	Max hosts scanned in parallel	`100`
`-sl, --socketLimit`	Max sockets open in total	`2048`
`-whl, --workersPerHostLimit`	Max worker threads per host	unlimited
`-do, --disableOnlineCheck`	Skip the host reachability check	false
`-sf, --showFilteredPorts`	Also show filtered ports	false
`-q, --quiet`	Suppress the progress output	false

Run with --help for the full reference.

License

jns is licensed under the GNU General Public License v3.0 or later.

See LICENSE for details.