What port is used by Java RMI connection

Question

May I know what port is used by Java RMI connection   If I want to connect a Java client application to a Java server application using RMI connection  what port I need to open at the server machine so that the client application can connect to it   I want to set up a firewall in the server machine but I don t know which port I should open

User · Answer

From the javadoc of java rmi registry Registry     Therefore  a registry s remote object implementation is typically exported with a well-known address  such as with a well-known ObjID and TCP port number  default is 1099     See more in the javadoc of java rmi registry LocateRegistry

User · Answer

In RMI  with regards to ports there are two distinct mechanisms involved     By default  the RMI Registry uses port 1099 Client and server  stubs  remote objects  communicate over random ports unless a fixed port has been specified when exporting a remote object  The communcation is started via a socket factory which uses 0 as starting port  which means use any port that s available between 1 and 65535

User · Answer

RMI generally won t work over a firewall  since it uses unpredictable ports  it starts off on 1099  and then runs off with a random port after that    In these situations  you generally need to resort to  tunnelling RMI over HTTP  which is described well here

User · Answer

If you can modify the client  then have it print out the remote reference and you will see what port it s using   E g   ServerApi server    ServerApi  registry lookup ServerApi RMI NAME   System out println  Got server handle     server     will produce something like   Got server handle Proxy ServerApi RemoteObjectInvocationHandler UnicastRef  liveRef   endpoint 172 17 3 190 9001 objID  -7c63fea8      where you can see the port is 9001   If the remote class is not specifying the port  then it will change across reboots   If you want to use a fixed port then you need to make sure the remote class constructor does something like   super rmiPort

User · Answer

The port is available here  java rmi registry Registry REGISTRY PORT  1099

User · Answer

With reference to other answers above  here is my view -  there are ports involved on both client and server side    for server remote side  if you export the object without providing a port   remote object would use a random port to listen  a client  when looks up the remote object  it would always use a random port on its side and will connect to the remote object port as listed above

User · Answer

All the answers so far are incorrect  The Registry normally uses port 1099  but you can change it  But that s not the end of the story  Remote objects also use ports  and not necessarily 1099   If you don t specify a port when exporting  RMI uses a random port  The solution is therefore to specify a port number when exporting  And this is a port that needs opening in the firewall  if any    In the case where your remote object extends UnicastRemoteObject  have its constructor call super port  with some non-zero port number  In the case where it doesn t extend UnicastRemoteObject  provide a non-zero port number to UnicastRemoteObject exportObject      There are several wrinkles to this    If you aren t using socket factories  and you provide a non-zero port number when exporting your first remote object  RMI will automatically share that port with subsequently exported remote objects without specified port numbers  or specifying zero  That first remote object includes a Registry created with LocateRegistry createRegistry    So if you create a Registry on port 1099  all other objects exported from that JVM can share port 1099  If you are using socket factories  your RMIServerSocketFactory must have a sensible implementation of equals   for port sharing to work  i e  one that doesn t just rely on object identity via    or Object equals    If either you don t provide a server socket factory  or you do provide one with a sensible equals   method  but not both  you can use the same non-zero explicit port number for all remote objects  e g  createRegistry 1099  followed by any number of super 1099  or exportObject      1099  calls

User · Answer

Depends how you implement the RMI  you can set the registry port  registry is a  unique point of services    If you don t set a explicit port  the registry will assume the port 1099 by default  In some cases  you have a firewall  and the firewall don t allow your rmi-client to see the stubs and objects behind the registry  because this things are running in randomically port  a different port that the registry use  and this port is blocked by firewall - of course  If you use RmiServiceExporter to configure your RmiServer  you can use the method rmiServiceExporter setServicePort port  to fixed the rmi port  and open this port in the firewall   Edit  I resolve this issue with this post  http   www mscharhag com java java-rmi-things-to-remember

User · Answer

You typically set the port at the server using the rmiregistry command  You can set the port on the command line  or it will default to 1099

[java] What port is used by Java RMI connection?

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