FAQs

Java Communications API FAQ

Thanks for the positive feedback on the Java communications API. Since we cannot reply individually, we have compiled an FAQ to help communicate with our customers/users.

Q: Will it be part of the JDK?

A: The Java communications API will be a Java Standard Extension, it will not be part of the core JDK.

Q: My application does not find any ports when it enumerates available ports.
Q: BlackBox gives me a message that says "No serial ports found!"

A: In order for the Java communications API to find ports the file javax.comm.properties must be in the correct place. The preferred location is in <jdk>/lib. See the installation instructions for alternate locations and further information.

Q: Can I load my own CommPort drivers, or am I limited to the provided Serial/Parallel drivers?

A: As a result of feedback, we have added this functionality. IMPORTANT: Use the Solaris implementation's comm.jar as a framework. See the CommDriver javadocs for details.

Q: Is there a linux version of the Java communications API?

A: We do not provide a linux implementation. But Kevin Hester has written Java communications API drivers for linux and uses our CommPort driver loading scheme to load his own gnu.io.RXTXCommDriver class. He gave us permission to disclose his web page:

http://www.geeksville.com/~kevinh/linuxcomm.html
http://wass.homelinux.net/howtos/Comm_How-To.shtml

Q: I would like to port the Java communications API to my favorite platform. Can you give me the source code to the reference implementations to help me out?

A: Sun will not be releasing the source code to reference implementations. Successful porting efforts are underway without the reference implementation source code (see previous answer).

Q: Will there be support for USB, Firewire or ISDN? How about higher level protocols such as X/Y/Z-modem or Kermit?

A: We are investigating adding support for other low-level communication protocols. But higher-level protocols such as X/Y/Z-modem or Kermit are outside of the focus of the Java communications API.

Q: How many listeners are allowed per instance of CommPort?

A: Currently the Java communications API supports one. Therefore, Parallel/SerialPort.removeEventListener() doesn't take any arguments.

Q: How does the CommPortIdentifier class relate to CommPort?

A: There is a one-to-one correspondence between a CommPortIdentifier object and a CommPort object. CommPortIdentifier provides functionality for discovering comm ports at init time, opening comm ports and managing ownership change events. The static method CommPortIdentifier.getPortIdentifier(String portName) returns a CommPortIdentifier instance with portName, while getPortIdentifiers() returns an enumeration of CommPortIdentifier objects that represent all the available ports.

Q: Can my app make direct reads from a port and also receive event notification on the same port?

A: Yes. Event notification is done with the lightweight JDK 1.1 event model. No data from the port is delivered with event notification. You will read from the port using CommPort.getInputStream().read().

Q: Can I use the Java communications API in applets?

A: Yes in signed applets, but no in unsigned applets (most cases). Since we do not allow unsigned applets access to any communications port under the JDK1.1 security model, you can not use the Java communications API with unsigned applets. We do plan to be compliant to JDK1.2 security model in later releases, which might allow trusted applet access to ports.

Q: I've edited my javax.comm.properties file and now my application cannot find any ports.

A: The javax.comm.properties file is not intended to be edited by users. If you are having problems after editing the file, we suggest that you reinstall the file.

Q: I've downloaded and installed the Java communications API. Now I have a great idea about an application that will use it. Can you tell me how to do the following...

A: The Java communications API team can not provide product support. We suggest that you use the Java Developer Connection (JDC). There are several avenues available in the JDC for getting answers to questions about how to use the Java communications API, including discussion groups with other developers. You must register to use the JDC, but there is no charge for registration.