On 9/30/2016 6:59 AM, Benjamin wrote:
Hello,
First I'd like to say I am really pleased with your course layout
thus far. I seem to be having a problem compiling your sample
multicast networking program on my mac.
Thanks for the kind words. I just tried MulticastServer and it compiled
and run fine.
The message below indicates that the compilation worked fine but
when you run it, the port 5000 cannot be assigned, which means
someone already uses the port.
Try "netstat -a |grep 5000" and see if port 5000 is already taken before you
run the app and kill the process that uses it.
-Sang
The exception/compiler output is as follows:
run:
MulticastSocket is created at port 5000
Exception in thread "main" java.net.SocketException: Can't assign
requested address
at java.net.PlainDatagramSocketImpl.join(Native Method)
at
java.net.AbstractPlainDatagramSocketImpl.join(AbstractPlainDatagramSocketImpl.java:179)
at java.net.MulticastSocket.joinGroup(MulticastSocket.java:323)
at MulticastChatServer.main(MulticastChatServer.java:27)
/Users/Benjamin/Library/Caches/NetBeans/8.1/executor-snippets/run.xml:53:
Java returned: 1
BUILD FAILED (total time: 0 seconds)
The code is:
import java.net.*;
public class MulticastChatServer {
public static void main(String args[])
throws Exception {
// Default port number we are going to use
int portnumber = 5000;
if (args.length >= 1) {
portnumber = Integer.parseInt(args[0]);
}
// Create a MulticastSocket
MulticastSocket serverMulticastSocket =
new MulticastSocket(portnumber);
System.out.println("MulticastSocket is created at port " +
portnumber);
// Determine the IP address of a host, given the host name
// The host name can either be a machine name, such as
"java.sun.com <http://java.sun.com/>",
// or a textual representation of its IP address. If a literal IP
// address is supplied, only the validity of the address
format is checked.
InetAddress group = InetAddress.getByName("225.4.5.6");
// getByName- returns IP address of given host
serverMulticastSocket.joinGroup(group);
System.out.println("joinGroup method is called...");
boolean infinite = true;
// Continually receives data and prints them
while (infinite) {
byte buf[] = new byte[1024];
DatagramPacket data =
new DatagramPacket(buf, buf.length);
serverMulticastSocket.receive(data);
String msg =
new String(data.getData()).trim();
System.out.println("Message received from client = " + msg);
}
serverMulticastSocket.close();
}
}
My network interface configuration is as follows:
Last login: Wed Sep 28 18:26:58 on ttys000
Benjamins-MacBook-Pro:~ Benjamin$ ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
options=3<RXCSUM,TXCSUM>
inet6 ::1 prefixlen 128
inet 127.0.0.1 netmask 0xff000000
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
nd6 options=1<PERFORMNUD>
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0<> mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether a4:5e:60:d9:ad:21
inet6 fe80::a65e:60ff:fed9:ad21%en0 prefixlen 64 scopeid 0x4
inet 192.168.1.10 netmask 0xffffff00 broadcast 192.168.1.255
nd6 options=1<PERFORMNUD>
media: autoselect
status: active
en1: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 4a:00:01:1f:c8:30
media: autoselect <full-duplex>
status: inactive
en2: flags=963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX> mtu 1500
options=60<TSO4,TSO6>
ether 4a:00:01:1f:c8:31
media: autoselect <full-duplex>
status: inactive
p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304
ether 06:5e:60:d9:ad:21
media: autoselect
status: inactive
awdl0: flags=8943<UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1484
ether de:39:ac:c0:e3:7c
inet6 fe80::dc39:acff:fec0:e37c%awdl0 prefixlen 64 scopeid 0x8
nd6 options=1<PERFORMNUD>
media: autoselect
status: active
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
options=63<RXCSUM,TXCSUM,TSO4,TSO6>
ether a6:5e:60:9d:fb:00
Configuration:
id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
ipfilter disabled flags 0x2
member: en1 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 5 priority 0 path cost 0
member: en2 flags=3<LEARNING,DISCOVER>
ifmaxaddr 0 port 6 priority 0 path cost 0
nd6 options=1<PERFORMNUD>
media: <unknown type>
status: inactive
utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1500
inet6 fe80::935a:dea6:fc62:3b81%utun0 prefixlen 64 scopeid 0xa
nd6 options=1<PERFORMNUD>
Benjamins-MacBook-Pro:~ Benjamin$ -Djava.net.preferIPv4Stack=true
-bash: -Djava.net.preferIPv4Stack=true: command not found
Benjamins-MacBook-Pro:~ Benjamin$
My basic computer info is in attachment:
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