RXTX - Full Java CommAPI implementation ======================================= This package contains a full implementation of the Java CommAPI from Sun. To use applications, written with the original CommAPI, with rxtx you have to change references to javax.comm.* to gnu.io.*. The rest of this file contains some useful information about problems with the rxtx package found in the upstream INSTALL file. The unimportant sections are left out. ------------------------------------------------------------------------------- 3. COMMON PROBLEMS [...] B. Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path librxtxSerial.so is located in the wrong directory. Here is an example $ mv /usr/local/java/jre/lib/i386/librxtxSerial* /usr/local/lib $ java BlackBox Exception in thread "main" java.lang.UnsatisfiedLinkError: no rxtxSerial in java.library.path at java.lang.ClassLoader.loadLibrary(Compiled Code) at java.lang.Runtime.loadLibrary0(Compiled Code) at java.lang.System.loadLibrary(Compiled Code) at gnu.io.NativePort.(NativePort.java:32) at gnu.io.RXTXPort.(Compiled Code) at gnu.io.RXTXCommDriver.getCommPort(Compiled Code) at gnu.io.CommPortIdentifier.open(Compiled Code) at SerialPortDisplay.openBBPort(Compiled Code) at SerialPortDisplay.(Compiled Code) at BlackBox.addPort(Compiled Code) at BlackBox.main(Compiled Code) ... lets fix it. Solution 1: move the file to a place that works $ mv /usr/local/lib/librxtxSerial.* /usr/local/java/jre/lib/i386/ Solution 2: add the location of librxtxSerial to LD_LIBRARY_PATH $ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/local/lib/ Solution 3: pass the location in on the command line $ java -Djava.library.path=/usr/local/lib/ ... C. I Can Not Open the Port. If you're not able to open the port (read the errors carefully) then you may not have permission to use the device. Redhat Linux ships with the following permissions: crw-r--r-- /dev/ttyS? Users need to be able to read and write with serial communication... chmod 666 /dev/ttyS? should fix the problem. Be sure to check the file CommAPI for common mistakes. Make sure that the user can create lock files. D. java.lang.NoClassDefFoundError: gnu/io/CommPort RXTXcomm.jar is probably not in your classpath or not located in the proper directory. for example, lets not include RXTXcomm.jar export CLASSPATH=../java/lib/classes.zip $ java BlackBoxException in thread "main" java.lang.NoClassDefFoundError: gnu/io/CommPort [...] H. BlackBox Can Not Handle all the ports! BlackBox has a hard coded limit in BlackBox.java that prevents it from running if you don't specify a port. We are considering alternative ways of handling the large number of port names in Unix. The line in question is: portDisp = new SerialPortDisplay[50]; just change 50 to say 256. I. Illegal use of nonvirtal function call! Exception in thread "main" java.lang.VerifyError: (class: gnu/io/RXTXPort$SerialOutputStream, method: flush signature: ()V) Illegal use of nonvirtual function call at gnu.io.RXTXCommDriver.getCommPort(Compiled Code) at gnu.io.CommPortIdentifier.open(Compiled Code) at SerialPortDisplay.openBBPort(Compiled Code) at SerialPortDisplay.(Compiled Code) at BlackBox.addPort(Compiled Code) at BlackBox.main(Compiled Code) "1.1 compilers sometimes generate code that won't verify under 1.2. If you don't have the sources for the offending class to recompile with a 1.2 javac, the only solution I know of is to launch the VM with the -noverify option. Louis" In other words start with a fresh build directory, rebuild, and reinstall to avoid the problem. [...] L. Problems with RMISecurityManager() Please see the file RMISecurityManager.html M. Which Wires Should be Connected? With the DB25 use 2 (TX), 3 (RX) and 7 (GD) to connect to the device. With the DB9 use 2 (RX), 3 (TX) and 5 (GD) to connect to the device. You will need to hook up more than that for hardware flow control. N. Which Device Should be Used? Linux serial ports should use /dev/ttyS? specialx, cyclades and isdn4 linux have been reported to work. as many as 64 ports have worked at one time. FreeBSD uses cuaa? netbsd uses tty0? Irix uses ttyd? ttym? ttyf? HP-UX uses tty0p? tty1p? BeOS uses /dev/ports/serial? Win32 uses COM? [...] P. Which jdk should be used? Ideally any jdk would be fine. Here is a list of jdk's tried on RedHat 6.0/kernel 2.2.17pre13 with various versions of glibc. Sun IBM Blackdown 2.1.2_006 1.3.0 1.1.8v1 green native green native green native ------------------------------------------ glibc-2.1.1-6 | OK | *1 | *2 | *2 | OK | *3 | ------------------------------------------- glibc-2.1.2-11 | OK | *1 | OK | OK | OK | OK | ------------------------------------------- glibc-2.1.2-17 | OK | *1 | OK | OK | OK | OK | ------------------------------------------- glibc-2.1.3-15 | OK | *1 | OK | OK | OK | OK | ------------------------------------------- 1) BlackBox (a demo application shipped with CommAPI locks after multiple open()/close() 2) java won't start "Unable to load /usr/local/java/jre/bin/libhpi.so: symbol sem_wait, version GLIBC_2.1 not defined in file libpthread.so.0 with link time reference Could not create the Java virtual machine." 3) java won't start "error in loading shared libraries: /usr/local/java/bin/../lib/i686/native_threads/libjava.so: symbol sem_init, version GLIBC_2.1 not defined in file libpthread.so.0 with link time reference" Conclusion? Avoid Sun's native threads unless you can figure out whats going wrong. Q. How does rxtx detect ports? Can I override it? rxtx tries to detect ports on by scanning /dev for files matching any of a set of known-good prefixes, such as 'ttyS', 'ttym', and so on. Any ones that exist, are supposed to be good for the current operating system, and that can be read and written are offered back from CommPortIdentifier.getPortIdentifiers(), and only these can be used as ports. If you wish, you can set the system properties gnu.io.rxtx.SerialPorts and gnu.io.rxtx.ParallelPorts. If either of these is set, then no scanning will be carried out and only the specified ports will be available. You can use this to make one platform look like another, to restrict Java access to ports, or possibly for other reasons. For example java -Dgnu.io.rxtx.SerialPorts=/dev/cua/a:/dev/cua/b com.foo.MyApp will look kind of like Solaris, if you have created the appropriate device nodes. A note on Linux port enumeration. We have set most ports aside. Once the number of possible devices started getting into the thousands, checking them all made little sense. Look in RXTXCommDriver.java and search for Linux. You will see that only /dev/ttyS* is searched but the possible addition ports that can be used are listed under it. Just copy the few you need. [...] S. How can I tell which version of rxtx is installed? Version information is not documented in Sun's CommAPI so this is probably unique to RXTX. As of rxtx-1.5-4 and rxtx-1.4-6 a class has been added to allow developers to check which version of rxtx is installed. The class is RXTXVersion. The static method: System.out.println(RXTXVersion.getVersion()); will print the rxtx version as a String in the following format: "RXTX-MAJOR.MINOR-PATCH". an example would be: "RXTX-1.5-4" A change in the MAJOR version would suggest you're in trouble. Odd MINOR version are reserved for development. Even MINOR versions are reserved for 'stable' releases. PATCH is used to differentiate incremental releases of the MINOR releases. CommPortIdentifier is expected to support getVersion() in the RXTX-1.5 series. T. What Type of Latency can I expect with RXTX frantz put RXTX under a scope and found the following: RXTX currently has a latency of 150-200ms on a PII at 450mhz. The latency can be reduced to 70-80ms by reducing the usleep() value in SerialImp.c:eventLoop() to usleep(5000)). Much lower latencies should be possible but the maintainer does not have equipment to test changes. He is going to look at this further. He needs 20 ms or less latency. U. I got rxtx working on a new OS but I can't read from the port > Now my java program starts up nicely without complaining. However, it does > never read any data from the serial port. It looks like it can write data, > because if I start a terminal program after I tried to run my program, I get > all the return stuff from the modem that my program wrote. > > I hacked around abit and found out that it hangs in the select() call which > simply never returns. > On Sun, 28 Jan 2001, Baldur Norddahl wrote: > HPUX 11: > > As I wrote to the mailinglist I had some weird problems where it apparently > could write data to the modem, but not read anything back. My terminal > programs had no problem using the port. A few days after I reported the > problem to the mailinglist, I had given up for now, but then I noticed that > it suddenly worked! So it remains a mystery what was wrong as I did not > change anything at all, neither in my program nor on the host. > > Baldur > I suspect two java applications had the port open. Its easy to do while developing. Perhaps z instead of c was entered. This is the reason for adding lockfile support to rxtx. If another application has opened the port, a second application will appear to not be able to read or get only part of the data. ..because the first one is reading. Only one of the select()s are waken. Its possible to put lockfile support in for HPUX if it is known where other applications place their lockfiles. The easiest way to find out where is to fire up minicom, kermit, ... and see where its lockfile is placed. Here are the known suspects: const char *lockdirs[]={ "/etc/locks", "/usr/spool/kermit", "/usr/spool/locks", "/usr/spool/uucp", "/usr/spool/uucp/", "/usr/spool/uucp/LCK", "/var/lock", "/var/lock/modem", "/var/spool/lock", "/var/spool/locks", "/var/spool/uucp",NULL }; freebsd uses /var/spool/uucp/, linux uses /var/lock those are the only two I've done so far. Adding the support is trivial once a directory is decided upon. Lockfiles are rather simple. when an application opens a port it first checks if there is a file with the ports name. If there is it grabs the PID from the file. If that PID is still active the application does not open the port. If the PID is not active or there is no lockfile, the application creates one with its own PID in it. The confusion starts when you have to decide where (see above) to put the lockfile, what the name format is for the file and how to store the PID. rxtx follows The File System Hierarchy Standard http://www.pathname.com/fhs/ on linux. I'm not positive what is normal on other OS's. more reading: The File System Hierarchy Standard http://www.pathname.com/fhs/ FSSTND ftp://tsx-11.mit.edu/pub/linux/docs/linux-standards/fsstnd/ Proposed Changes to the File System Hierarchy Standard ftp://scicom.alphacdc.com/pub/linux/devlock-0.X.tgz "UNIX Network Programming", W. Richard Stevens, Prentice-Hall, 1990, pages 96-101. more reading: V. My ThinkPad is Not Working! Scott Burleigh writes: For your files, and in case anybody asks in the future, IBM Thinkpads ship with the external serial port *disabled* by default. The Thinkpad configuration utility supplied with the machine (under Windows) says it's enabled, and the device manager in the System dialog of the Control panel says it's enabled, but they lie. In order to enable the port you have to use the old DOS ps2.exe bios configuration utility which, under Windows 2000, is in c:\Program Files\Thinkpad\utilities: ps2 sera enable Until you do, "setserial -ga /dev/ttyS0" will always tell you the UART is unknown. 4. APPLETS More info is needed on signing applets. This is an exchange from the rxtx mail- list. A. Using Applets prashantg10@yahoo.com asked: Hi All ! I am trying to use applet on thin terminal which has Linux base Kernel.For testing I am using Linux machine.I have install all the required components. e.g. JDK, RXTX. Everything is fine. BlackBox runs ,even my application runs. When It comes to applet, everything is halts. It does not even show the listing of ports. Is it because applet can't run under root account or what might be the reasons. Can anybody tell me solution. Son To replied: Java applets run within the sandbox of the security manager. Applets must be signed to access the com port, but for development purposes you can put user_pref("signed.applets.codebase_principal_support", true); in your prefs.js located in ~/.mozilla/default/XYYrandomDirName I didn't use Java applet for my application. I used XUL and CSS for the GUI development and used mozilla Javascript SOAP library to communicate with apache Axis webservice backend which uses RXTX to access the com port. ------------------------------------------------------------------------------- -- Mario Jou/3en