AISmessages is a Java-based light-weight, zero-dependency, and ultra-efficient message decoder for maritime navigation and safety messages compliant with ITU 1371 (NMEA armoured AIS messages).

Internally AISmessages uses eager parsing and a fail‑fast design combined with immutable value objects. This minimizes runtime surprises and allocation churn, reduces the need for synchronization, and makes message instances safe to share across threads — ideal for high‑throughput, concurrent, or real‑time applications (including non‑blocking/reactive systems). The library’s low‑allocation, zero‑dependency implementation yields predictable performance and low GC impact under heavy load. It fully decodes tens of thousands of NMEA armoured AIS messages per second per CPU core on an Intel i7-based laptop.

Version 4 Performance: AISmessages v4 represents a major architectural improvement over earlier versions. By switching from lazy decoding (used in v2.x-3.x) to eager parsing with immutable value objects, v4 dramatically reduces garbage collection pressure and memory churning. The eager approach eliminates the WeakReference overhead and repeated parsing of previous versions, resulting in predictable upfront allocation, zero post-construction allocations, and significantly lower GC overhead — especially beneficial for high-throughput scenarios processing thousands of messages per second.

For more than 15+ years AISmessages has been used in production in many systems and solutions all over the world.

If you are new to AIS you can read a short introduction to it on my blog.

In addition to AISmessages, its sister project AISutils offers higher level functionality such as Tracking and Filtering using AISmessages as a foundation.

There is also AIScli which allows conversion, filtering, etc. of AIS messages from the command line. AIScli is built on top of both AISmessages and AISutils.

There are several demos, intros, and public appearances of AISmessages; like for instance:

1. How AISmessages is utilized by OpenRemote, Inc. for the Safe Waterways project in the Beatrix Canal, NL, as explained in this Youtube video:
   

2. How AISmessages is used in Dakosy's PRISE system to optimise sequencing and arrival of mega-ships on the river Elbe and at the Port of Hamburg (read reference page)

3. How AISmessages can be used to "decode the air around you" as Bert Jan Schrijver (@bjschrijver) of JPoint talks about

   1. at DEVOXX BE 2015 (watch conference video)
   2. at DEVOXX UK 2015 (watch conference video)

4. A live demo of AISmessages is available on http://ais.tbsalling.dk.

5. See a simple demo applications in the source code in the dk.tbsalling.aismessages.demo package (view via Github).

6. AISMessages is used by Pronto, which enables the Port of Rotterdam to optimize port calls and vessel operations.

7. AISMessages is used by Shiptracker, which enables Port of Rotterdam to show its customers the current position and ETA of ships scheduled to arrive in the port.

Programmatically the starting point is the AISStreamReader. It takes an InputStream (feeding NMEA data), and a consumer of AISMessages which as called back every time an AIS message is decoded. So, if you have an InputStream serving data like this:

    !AIVDM,1,1,,A,15Mv5v?P00IS0J`A86KTROvN0<5k,0*12
    !AIVDM,1,1,,A,15Mwd<PP00ISfGpA7jBr??vP0<3:,0*04
    !AIVDM,2,1,4,B,55MwW7P00001L@?;GS0<51B08Thj0TdpE800000P0hD556IE07RlSm6P0000,0*0B
    !AIVDM,2,2,4,B,00000000000,2*23
    !AIVDM,1,1,,A,15N7th0P00ISsi4A5I?:fgvP2<40,0*06
    !AIVDM,1,1,,A,15NIEcP000ISrjPA8tEIBq<P089=,0*63
    !AIVDM,1,1,,B,15MuS0PP00IS00HA8gEtSgvN0<3U,0*61
    \c:1609841515,s:r3669961*78\!AIVDM,1,1,,A,13ukmN7@0<0pRcHPTkn4P33f0000,0*58
    \c:1609841515,s:r3669961,g:1-2-1234*0E\!AIVDM,1,1,,A,13ukmN7@0<0pRcHPTkn4P33f0000,0*58

then you can decode it into Java POJO's of type AISMessage like this:

    public class DemoApp {

        public static void main(String[] args) throws IOException {

           InputStream inputStream = ...

           AISInputStreamReader streamReader
                = new AISInputStreamReader(
                    inputStream,
                    aisMessage -> System.out.println(aisMessage))
           );

           streamReader.run();
	    }

    }

The second argument to the AISInputStreamReader constructor (aisMessage -> System.out.println(aisMessage)) is a Consumer<? super AISMessage> which consumes decoded AIS messages in the form of AISMessage objects.

AISMessage has several subclasses - one for each type of AIS message, which can be decoded. For instance an AIS message of type 5 "Static and voyage related data" are represented by objects of class ShipAndVoyageData as shown here in fragments:

public class ShipAndVoyageData extends AISMessage implements StaticDataReport {
    ...
    public IMO getImo() { ...}
    public String getCallsign() { ...}
    public String getShipName() { ...}
    public ShipType getShipType() { ...}
    public int getToBow() { ...}
    public int getToStern() { ...}
    public int getToStarboard() { ...}
    public int getToPort() { ...}
    ...
}

AISmessages supports decoding of Application Specific Messages (ASM) transmitted via AIS messages type 6 (addressed binary message) and type 8 (binary broadcast message). These messages carry specialized information according to various standards.

The library implements the 24 standardized application-specific messages defined by IMO SN.1/Circ.289 for international use (Designated Area Code = 001):

• DAC=200, FI=10: Inland Ship Static and Voyage Related Data (InlandShipStaticAndVoyageRelatedData)

Application Specific Messages can be accessed from the parent binary message:

BinaryBroadcastMessage binaryMessage = (BinaryBroadcastMessage) aisMessage;
ApplicationSpecificMessage asm = binaryMessage.getApplicationSpecificMessage();

if (asm instanceof WeatherObservation weather) {
    System.out.println("Temperature: " + weather.getAirTemperature());
    System.out.println("Wind Speed: " + weather.getAverageWindSpeed());
    // ... access other weather data
}

Unknown or unsupported application specific messages are represented as UnknownApplicationSpecificMessage, which provides access to the raw binary data.

AISmessages also supports receiving AIS messages via UDP, which is a common method for receiving AIS data from various sources. Here's how to use it:

import dk.tbsalling.aismessages.ais.messages.AISMessage;
import dk.tbsalling.aismessages.nmea.NMEAMessageHandler;
import dk.tbsalling.aismessages.nmea.NMEAMessageUDPSocket;

public class UDPExample {
    public static void main(String[] args) {
        try {
            NMEAMessageUDPSocket udpSocket = new NMEAMessageUDPSocket(
                "127.0.0.1",  // Host address to bind to
                10110,        // UDP port to listen on
                new NMEAMessageHandler("UDPSRC", aisMessage -> {
                    // Process each received AIS message
                    System.out.println("Received: " + aisMessage);
                })
            );
            udpSocket.run();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

The UDP receiver will bind to the specified host and port and process incoming UDP packets containing NMEA-formatted AIS messages. You can stop the receiver by calling udpSocket.requestStop().

A complete demo application is available in the dk.tbsalling.aismessages.demo.UDPDemoApp class.

You do not need to compile AISmessages yourself. It is available in Maven Central. So if you are using Maven, all you need to do is add these lines to your pom.xml:

...
<dependency>
    <groupId>dk.tbsalling</groupId>
    <artifactId>aismessages</artifactId>
    <version>4.1.0</version>
</dependency>
...

AISmessages is released under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) license - which means that it is free for non-commercial use. For full license details see the LICENSE file.

AISmessages (C) Copyright 2011- by S-Consult ApS, VAT no. DK31327490, Denmark.

AISmessages is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 Unported License.

To obtain an alternative commercial license and/or support contact Thomas Borg Salling - [email protected].