TCP Server And Client Example model give ConcurrentModificationException

[hqnghi88]

To Reproduce
Steps to reproduce the behavior:

1. Go to Plugins models \Network\2 Available protocols\TCP protocol\TCP Server And Client Example .gaml
2. Launch experiment.
3. See error
   2 occurrences in 2 agents at cycle 1: Java error: ConcurrentModificationException
   in write (name + ' received : ') + mm.contents color: color ;
   ConcurrentModificationException: null
   java.base/java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1486)
   java.base/java.util.TreeMap$KeyIterator.next(TreeMap.java:1540)
   com.thoughtworks.xstream.core.util.PrioritizedList$PrioritizedItemIterator.next(PrioritizedList.java:91)
   com.thoughtworks.xstream.core.DefaultConverterLookup.lookupConverterForType(DefaultConverterLookup.java:73)
   com.thoughtworks.xstream.XStream$1.lookupConverterForType(XStream.java:472)
   com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:56)
   com.thoughtworks.xstream.core.TreeUnmarshaller.convertAnother(TreeUnmarshaller.java:50)
   when applying the contents operator on ummisco.gama.network.common.CompositeGamaMessage@7b6c7db2
   in write (name + ' received : ') + mm.contents color: color ;
   in loop while: self.has_more_message() {
   message mm <- self.fetch_message();
   write (name + ' received : ') + mm.contents color: color ;
   }

in reflex receive when: self.has_more_message() {
loop while: self.has_more_message() {
message mm <- self.fetch_message();
write (name + ' received : ') + mm.contents color: color ;
}

}

in agents Server0, Simulation 0

However the TCP Teleportation still works well.

Expected behavior
No error

gama git 1.8.2, win 11

[hqnghi88]

@AlexisDrogoul @gnoubi @benoitgaudou i tried a solution that provide the xstream by class, for thread safe. It seems to work, but i tested only network model, not the serialized Experiment. So it require a clear review and reimplementation as Alexis said in #3288 " one instance per agent / model / message sending/receiving,"

[benoitgaudou]

tested and seems to work. Thanks !