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© 2021, V10.4
 
  Jython
 
 

 

Computer communication is a fascinating and motivating subject in every informatics course because it is more and more relevant in everyday life due to the importance of the internet and the widespread if interacting systems at home. The most important communication protocol for computer systems is clearly TCP/IP. Programming TCP/IP is also called socket programming.

Socket programming is based on the client/server model, where a server system is started first and is waiting (looking for) a client system that requests a connection. After the connection link is established we say that a socket is opened and stream typed data are exchanged. To break the communication link, we say that the socket is closed.

Socket programming requires knowledge of threads and streams and a good understanding of synchronizing interacting systems. With TCP/IP there is a additional problem that systems on the internet cannot use plain sockets because of firewall protection. To solve this problem data transmission has to be "tunneled" using the HTTP protocol. To hide this additional complexity the TcpJLib package has been developed (see here for more information)

TcpJLib can be used with Java as well as with Jython with no change. Thus porting programs from Java to Jython and vice versa is rather straightforward. If you are looking for more examples and ideas than presented on this page, consult the TcpJLib tutorial and example pages. The documentation may help too.

To use TcpJLib with the TigerJython IDE, download the distribution from here and copy TcpJLib.jar in the Lib subdirectory of the IDEs <home> directory. Append the library file to the sys path with

import sys
sys.path.append("./Lib/TcpJLib.jar")

The first examples uses two TcpNodes that exchange string data. The GUI is rudimentary but it shows the basics of a chat system where two (or more) people exchange text messages.

Error Page

Error Page

Stack trace:

java.io.FileNotFoundException: The requested resource [/home/pyincludes/TcpChat.html] is not available
	at org.apache.catalina.servlets.DefaultServlet.serveResource(DefaultServlet.java:845)
	at org.apache.catalina.servlets.DefaultServlet.doGet(DefaultServlet.java:497)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
	at org.apache.catalina.servlets.DefaultServlet.service(DefaultServlet.java:477)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.jython_005fex7_jsp._jspService(jython_005fex7_jsp.java:165)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:712)
	at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:580)
	at org.apache.catalina.core.ApplicationDispatcher.access$100(ApplicationDispatcher.java:64)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:113)
	at org.apache.catalina.core.ApplicationDispatcher$PrivilegedInclude.run(ApplicationDispatcher.java:101)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:507)
	at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:955)
	at org.apache.jsp.apluhomex_jsp._jspService(apluhomex_jsp.java:2358)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:477)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
	at sun.reflect.GeneratedMethodAccessor29.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:170)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:225)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at sun.reflect.GeneratedMethodAccessor31.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:282)
	at org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:279)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAsPrivileged(Subject.java:549)
	at org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:314)
	at org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:253)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:191)
	at org.apache.catalina.core.ApplicationFilterChain.access$000(ApplicationFilterChain.java:47)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:149)
	at org.apache.catalina.core.ApplicationFilterChain$1.run(ApplicationFilterChain.java:145)
	at java.security.AccessController.doPrivileged(Native Method)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:144)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
	at org.apache.coyote.ajp.AjpProcessor.service(AjpProcessor.java:432)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

Request URL:

https://aplu.ch/home/apluhomex.jsp

Parameters:

    site: 138