AppletTalk.com Java discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  udp client: destination port unreachable question          AppletTalk.com Forum Index -> Java Language Programming View previous topic :: View next topic   Author Message Guest Posted: Sun May 13, 2007 6:59 am    Post subject: udp client: destination port unreachable question Hello, My question is concerned with java.net package. I used trivial UDPClient example to send datagrams from local interface eth1 on Linux to the ip host not included into local route table and I tried to capture outgoing udp traffic on interface eth1. I've got IOException "ICMP: destination unreachable" and I only could capture outgoing packets on loopback interface ( with Ethereal). Can someone help to resolve my confusion: I thought UDP is "connectionless", e.g. will be sent regardless. What does ICMP have to do with it and why does this traffic appear on loopback interface? Thank you, Back to top Esmond Pitt Guest Posted: Sun May 13, 2007 7:11 am    Post subject: Re: udp client: destination port unreachable question vlyamtsev (AT) gmail (DOT) com wrote: Quote: Hello, My question is concerned with java.net package. I used trivial UDPClient example to send datagrams from local interface eth1 on Linux to the ip host not included into local route table and I tried to capture outgoing udp traffic on interface eth1. I've got IOException "ICMP: destination unreachable" and I only could capture outgoing packets on loopback interface ( with Ethereal). Can someone help to resolve my confusion: I thought UDP is "connectionless", e.g. will be sent regardless. What does ICMP have to do with it and why does this traffic appear on loopback interface? err, because the destination host is unreachable? Where would you expect UDP to send the packet *to* if there is no unicast route to the target? You get the ICMP response if you have used DatagramSocket.connect(). If you avoid that and put the destination address into the DatagramPacket, you won't get the exception, but the packet still won't go out as there is no unicast route. If that's what you want. Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         AppletTalk.com Forum Index -> Java Language Programming All times are GMT Page 1 of 1   Jump to: Select a forum Java Newsgroups----------------Java DiscussionsWeb-based java games comp.lang.java 3D Graphics API's for Java Java: Support and criticism Java System Announcements comp.lang.java.api JavaBeans Java and CORBA Java and Databases comp.lang.java.developer Java GUI Toolkits Java Help comp.lang.java.javascript JVM, native methods and hardware comp.lang.java.misc Java Language Programming Security and Java comp.lang.java.setup Java Software Tools comp.lang.java.tech ibm.software.java.linux  Non-English Java Newsgroups----------------Java Language (German)Language Java (Français)Java (Italian)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.