1. Client-Server Communication
Sockets
Remote Procedure Calls
Remote Method Invocation (Java)

2. Sockets A socket is defined as an endpoint for communication
Concatenation of IP address and port
The socket :1625 refers to port 1625 on host
Communication consists between a pair of sockets
Low level: Sends/receives a stream of bytes.
Sockets are either connection-oriented (i.e., TCP) or connectionless (i.e., UDP).

3. Socket Communication

4. Remote Procedure Calls
Remote procedure call (RPC) abstracts procedure calls between processes on networked systems.
Stubs – client-side proxy for the actual procedure on the server.
The client-side stub locates the server and marshalls the parameters.
The server-side stub receives this message, unpacks the marshalled parameters, and performs the procedure on the server.
Returns output of procedure (if applicable).

5. Remote Method Invocation
Remote Method Invocation (RMI) is a Java mechanism similar to RPCs.
RMI allows a Java program on one machine to invoke a method on a remote object.
Can send objects to remote JVM

6. Single and Multithreaded Processes

7. Benefits Responsiveness (e.g., Web server).
Resource Sharing (several threads of control within a common address space).
Economy (threads are often termed lightweight processes). Much cheaper to create and manage.
Utilization of MP Architectures

8. User vs Kernel Threads User Threads: Kernel Threads:
Thread management done by user-level threads library.
When one thread blocks, the process blocks.
Kernel Threads:
Supported by the kernel.
When one thread blocks the OS can pick another thread within the same process to execute.
Allows overlapping of (for example) computation and I/O requests.

9. Kernel Threads Examples Windows XP/2000 Solaris Linux Tru64 UNIX
Mac OS X

10. Multithreading Models
Many-to-One
One-to-One
Many-to-Many

11. Many-to-One Many user-level threads mapped to single kernel thread.
Possible to overlap I/O computation?
Examples:
Solaris Green Threads
GNU Portable Threads

12. Many-to-One Model

13. One-to-One Each user-level thread maps to kernel thread Examples
Windows NT/XP/2000
Linux
Solaris 9 and later

14. One-to-one Model

15. Many-to-Many Model
Allows many user level threads to be mapped to many kernel threads
Allows the operating system to create a sufficient number of kernel threads
Solaris prior to version 9
Windows NT/2000 with the ThreadFiber package

16. Many-to-Many Model

17. Two-level Model
Similar to M:M, except that it allows a user thread to be bound to kernel thread
Examples
IRIX
HP-UX
Tru64 UNIX
Solaris 8 and earlier

18. Two-level Model