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Java I/O FAQ   

This page is the FAQ for the "I/O and Streams" forum. It's editable by everyone, so add your own content as you see fit.

Other FAQ pages that deal with I/O

  • The FileUpload page has hints on how to upload files to a server via FTP, SMB and HTTP.

  • WhoisLookup - how to perform a whois lookup programmatically



Links to articles elsewhere that relate to I/O

  • Using ICMP packets (for ping and traceroute) in Java: Jpcap library

  • JNetPcap - library for network packet capture and analysis


Where can I get an implementation of the javax.comm API for Windows?

Sun does not provide an implementation of javax.comm version 3 for Windows, but version 2 can be used in conjunction with RXTX; see the javax.comm download page for further information. Other options (which do not implement the javax.comm API) are

  • RXTX (open source)
  • icaste JCommSerial (commercial)
  • SerialPort (commercial, X/Y/ZModem and Kermit implementations are also available)


How can I set the client timeout when making an URL connection?

Starting with Java 5, this functionality is available in the JavaDoc:java.net.URLConnection class and its subclasses (like HttpURLConnection) via the getConnectTimeout/setConnectTimeout methods.

Jakarta Commons HttpClient also supports setting a timeout.


How can I check the type of an image file?

The freely available ImageInfo class can identify certain image types: JPEG, PNG, GIF, BMP, PCX, IFF, RAS, PBM, PGM, PPM and PSD. It also determines certain image properties like height, width and color depth.


How can I send SMS from a Java application?

You'll need an SMS library like smsj, SMSLib or smstools and a provider. You can find the latter by googling for "bulk sms http". This article may also be of interest.

Many cellular providers make an email-to-SMS gateway available. Here are the email addresses for several US providers:

  • T-Mobile: phonenumber@tmomail.net
  • Virgin Mobile: phonenumber@vmobl.com
  • Cingular: phonenumber@cingularme.com
  • Sprint: phonenumber@messaging.sprintpcs.com
  • Verizon: phonenumber@vtext.com
  • Nextel: phonenumber@messaging.nextel.com

where phonenumber = your 10 digit phone number

I would probably not use this gateway for bulk message as the providers no doubt have measures in place to prevent abuse.


How can I use a modem from within Java? (or, to put it in another way, is there an implementation of JTAPI?)

The http://xtapi.sourceforge.net/ project "has providers for Microsoft’s TAPI, Serial Voice Modems, and Voice Over IP utilizing the OpenH323? Projects H.323 stack implementation".


How can I determine the encoding of a given file, or its MIME type?

The jchardet and juniversalchardet libraries try to determine the encoding. This article talks about various approaches to figure out the MIME type; you may have to try out a few of them to determine which one works best in your situation.


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