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A client-server system is a distributed computing architecture where multiple clients request services from centralized servers over a network. Communication in client-server systems can utilize shared memory and message passing techniques, along with several specialized communication strategies. Strategies for Communication There are three primary strategies for communication in client-server systems − Sockets A socket is defined as an endpoint for communication. A pair of processes communicating over a network employs a pair of sockets, one for each process. A socket is identified by an IP address concatenated with a port number. Sockets generally use client-server ... Read More
Marshalling in RPC (Remote Procedure Call) is the process of converting procedure arguments and return values into a format suitable for network transmission. When a client makes a remote procedure call, the parameters must be packaged (marshalled) into a message, sent across the network, and then unpacked (unmarshalled) on the server side. How RPC Works Remote Procedure Call (RPC) is a client-server mechanism that enables an application on one machine to make a procedure call to code on another machine. The client calls a local procedure—a stub routine—that packs its arguments into a message and sends them across ... Read More
Secure Shell (SSH) is a network protocol that allows secure remote connections between two systems. It is commonly used to access and manage Linux servers remotely. However, SSH sessions can be terminated due to network timeouts, inactivity, or connection drops, which can be frustrating during long-running tasks. This article discusses various methods to keep SSH sessions alive on Linux systems. Server-Side Configuration Using ClientAliveInterval Option The most effective way to prevent SSH sessions from timing out is to configure the SSH server to send keep-alive packets. This is done using the ClientAliveInterval option in the SSH server ... Read More
During our daily use of Linux, we may want to check if there are any changes to any of the files in a directory. Or we might want to confirm that the contents of one directory are the same as those of another directory on a different location, disk, or system. In this tutorial we will learn how to compute an MD5 checksum of an entire directory tree on Linux. We will compute a single hash value of all directory contents for comparison purposes. Get the List of All Files in a Directory Tree To find out the ... Read More
When it comes to working with command-line utilities in Linux, there are many tools and utilities available that can make your life easier. One such utility is xargs, a command that allows you to execute commands on a list of files, or arguments, from standard input. Xargs is particularly useful when you want to perform an operation on a large number of files, and you want to do it quickly and efficiently. In this article, we will discuss various scenarios where you may need to use xargs in Linux. We will also look at some examples to illustrate how ... Read More
MySQL ERROR 1819 (HY000) is a common error that occurs when attempting to create or modify a MySQL user account with a password that doesn't meet the server's security policy requirements. The error message typically reads: "Your password does not satisfy the current policy requirements". Why Does MySQL ERROR 1819 Occur? This error occurs primarily due to MySQL's password validation plugin, which enforces strict password policies to enhance security. The plugin was introduced in newer MySQL versions and requires passwords to meet specific criteria such as: Minimum length requirements (typically 8 characters) Use of uppercase and ... Read More
Linux manages thread allocation through several system parameters and limits. The maximum number of threads per process is determined by multiple factors including system-wide thread limits, virtual memory availability, and stack size configurations. System-Wide Thread Limit The first approach to check the maximum number of threads is to examine the system-wide limit: cat /proc/sys/kernel/threads-max 61741 This value represents the total number of threads that can exist on the entire system. You can modify this limit using: echo 123456789 > /proc/sys/kernel/threads-max where 123456789 is your desired maximum thread ... Read More
Operating Systems have become quite complex and multifaceted with the advancement of time. However, that also means it is getting more and more difficult to design operating systems that satisfy all the specifications required these days. There are no complete solutions possible for design problems, but some approaches are more successful than others. Design Requirements in Operating System The design requirements are quite hard to specify in an operating system. They are basically divided into two parts: User design requirements and System design requirements. Details about these are given as follows − User Design Requirements The ... Read More
The Dining Philosophers Problem (DPP) is a classic synchronization problem in computer science that illustrates the challenges of deadlock and resource sharing in concurrent systems. The problem states that there are 5 philosophers sharing a circular table where they eat and think alternatively. There is a bowl of rice for each philosopher and 5 chopsticks placed between them. A philosopher needs both their right and left chopstick to eat. A hungry philosopher may only eat if both chopsticks are available, otherwise they put down any chopstick they hold and begin thinking again. This problem demonstrates a large class of ... Read More
Advanced Local Procedure Call (ALPC) is a high-performance message-passing mechanism in Windows that enables efficient inter-process communication (IPC) between client and server processes. ALPC replaced the older Local Procedure Call (LPC) mechanism and provides optimized communication channels with multiple message-passing techniques based on data size requirements. How ALPC Works The ALPC mechanism follows a client-server communication model. The server process publishes a globally visible connection-port object that clients can access to request services. When a client needs services from a subsystem, it opens a handle to the server's connection-port and sends a connection request. ... Read More