Previously DaMSA/AisLib
DMA AisLib is a Java library for handling AIS messages. This include
- Reading from AIS sources e.g. serial connection, TCP connection or file
- Handling of proprietary source tagging sentences
- Message filtering like doublet filtering and down sampling
- Decoding sentences and AIS messages
- Encoding sentences and AIS messages
- Sending AIS messages #6, #8, #12 and #14
- Handling application specific messages
The library contains test code and utility applications demonstrating the use.
The project is separated into three parts:
- Java 1.7
- Maven 3
- e-Navigation https://github.com/dma-dk/e-Navigation
To build everything
mvn install
To run tests
mvn test
mvn eclipse:eclipse
Import into Eclipse
You're encouraged to contribute to AisLib. Fork the code from https://github.com/dma-dk/AisLib and submit pull requests.
This library is provided under the LGPL, version 3.
Reading from files or TCP connections is very simple with AisLib. In the example below messages are read from a file.
AisReader reader = new AisStreamReader(new FileInputStream("sentences.txt"));
reader.registerHandler(new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
System.out.println("message id: " + aisMessage.getMsgId());
}
});
reader.start();
reader.join();Reading using a TCP connection is just as easy
AisTcpReader reader = new AisTcpReader("localhost", 4001);
reader.registerHandler(new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
System.out.println("message id: " + aisMessage.getMsgId());
}
});
reader.start();
reader.join();If the connection is broken the reader will try to reconnect after a certain amount of time that can be set with:
reader.setReconnectInterval(1000);A read timeout can be defined for the reader. If no data is received within this period the connection will be closed and a reconnect will be tried.
Instead of working with AisMessage objects, it is possible to work with unparsed raw message packets (proprietary tags, comment blocks and VDM's).
AisTcpReader reader = new AisTcpReader("localhost", 4001);
reader.registerPacketHandler(new Consumer<AisPacket>() {
@Override
public void accept(AisPacket aisPacket) {
}
});
reader.start();
reader.join();To determine what messages are received the instanceof operator can be used. The example below shows how to test and cast, and take advantage of the object oriented design where related messages shares parents.
@Override
public void accept(AisMessage aisMessage) {
// Handle AtoN message
if (aisMessage instanceof AisMessage21) {
AisMessage21 msg21 = (AisMessage21) aisMessage;
System.out.println("AtoN name: " + msg21.getName());
}
// Handle position messages 1,2 and 3 (class A) by using their shared parent
if (aisMessage instanceof AisPositionMessage) {
AisPositionMessage posMessage = (AisPositionMessage)aisMessage;
System.out.println("speed over ground: " + posMessage.getSog());
}
// Handle position messages 1,2,3 and 18 (class A and B)
if (aisMessage instanceof IGeneralPositionMessage) {
IGeneralPositionMessage posMessage = (IGeneralPositionMessage)aisMessage;
System.out.println("course over ground: " + posMessage.getCog());
}
// Handle static reports for both class A and B vessels (msg 5 + 24)
if (aisMessage instanceof AisStaticCommon) {
AisStaticCommon staticMessage = (AisStaticCommon)aisMessage;
System.out.println("vessel name: " + staticMessage.getName());
}
}The example below shows how messages from multiple sources can be handled by a single handler.
// Make a handler
IAisHandler handler = new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
System.out.println("aisMessage: " + aisMessage);
}
};
// Make readers and register handler
AisReader reader1 = new AisTcpReader("host1", 4001);
AisReader reader2 = new AisTcpReader("host2", 4001);
AisReader reader3 = new AisTcpReader("host3", 4001);
reader1.registerHandler(handler);
reader2.registerHandler(handler);
reader3.registerHandler(handler);
// Start readers
reader1.start(); reader2.start(); reader3.start();The example below shows how to round robin between TCP hosts. If one goes down, the re-connect will be to the next on the list.
RoundRobinAisTcpReader reader = new RoundRobinAisTcpReader();
reader.addHostPort("host1:4001");
reader.addHostPort("host2:4001");
reader.addHostPort("host3:4001");
reader.registerHandler(new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
System.out.println("message id: " + aisMessage.getMsgId());
}
});
reader.start();
reader.join(); Message filters implement a single method
boolean rejectedByFilter(AisMessage message);
Down sample example:
RoundRobinAisTcpReader reader = new RoundRobinAisTcpReader();
reader.setCommaseparatedHostPort("ais163.sealan.dk:4712");
reader.registerHandler(new Consumer<AisMessage>() {
DownSampleFilter downSampleFilter = new DownSampleFilter(60);
@Override
public void accept(AisMessage aisMessage) {
if (downSampleFilter.rejectedFilter(aisMessage)) {
return;
}
// Handle message
}
});
reader.start();
reader.join(); A MessageHandlerFilter can be used to put in between readers and handlers. In the example below two filters are used. A doublet filter and a down sampling filter.
IAisHandler handler = new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
// Handle doublet filtered down sampled messages
}
};
// Make down sampling filter with sampling rate 1 min and
// make handler the recipient of down sampled messages
MessageHandlerFilter downsampleFilter = new MessageHandlerFilter(new DownSampleFilter());
downsampleFilter.registerReceiver(handler);
// Make doublet filter with default window of 10 secs.
// Set down sample filter as recipient of doublet filered messages
MessageHandlerFilter doubletFilter = new MessageHandlerFilter(new DuplicateFilter());
doubletFilter.registerReceiver(doubletFilter);
// Make reader
AisReader reader = new AisTcpReader(host, port);
reader.registerHandler(doubletFilter);
reader.start();AisLib can handle some proprietary tags inserted before VDM sentences, but implementations of factories must be given. In the example below Gatehouse source tags are handled.
Proprietary factories are defined in the file
ais-lib-messages/src/main/resources/META-INF/services/dk.dma.ais.proprietary.ProprietaryFactory
AisReader reader = new AisStreamReader(new FileInputStream("sentences.txt"));
reader.registerHandler(new Consumer<AisMessage>() {
@Override
public void accept(AisMessage aisMessage) {
if (aisMessage.getSourceTag() != null) {
IProprietarySourceTag sourceTag = aisMessage.getSourceTag();
System.out.println("timestamp: " + sourceTag.getTimestamp());
}
}
});
reader.start();
reader.join();Example of sending an addressed text message in an ABM sentence. See test cases on how to send application specific message. See AisReader for different sending options. In the example below all ABM packaging is handled by AisReader.
AisReader aisReader = new AisTcpReader(host, port);
aisReader.start();
...
// Make AIS message 12
AisMessage12 msg12 = new AisMessage12();
msg12.setDestination(destination);
msg12.setMessage(message);
// Send using a blocking call
Abk abk = aisReader.send(msg12, 1, destination);
if (abk.isSuccess()) {
...
} else {
...
}