JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III NETWORK PROGRAMMING Previous Question Paper (February - 2023 - R18)

A concurrent server is a network server architecture designed to handle multiple client requests simultaneously rather than processing them sequentially. Instead of blocking the main server process while waiting for a single client to finish its task, the server employs concurrency mechanisms to manage multiple connections in parallel.

The typical operation of a concurrent server involves the following steps:

• The server process listens for incoming connection requests on a well-known port.
• Upon receiving a request, the server accepts the connection and immediately spawns a separate child process or thread to handle the specific client session.
• The parent process returns to the listening state to accept new incoming connections, while the child process handles the communication with the assigned client.
• This approach significantly improves server throughput and responsiveness, as the server does not remain idle while waiting for I/O operations from a single client.

Common techniques used to implement concurrent servers include:

• Multi-processing: Using the fork() system call to create a new process for each client.
• Multi-threading: Using libraries like POSIX threads (pthreads) to create lightweight execution units within the same process space.
• I/O Multiplexing: Using system calls like select(), poll(), or epoll() to monitor multiple file descriptors simultaneously within a single process.

To determine the host byte order, one must check how a multi-byte integer is stored in memory. By storing a known value, such as 0x0001, in a 2-byte integer and inspecting the first byte in memory, we can identify whether the system is Little-Endian (where the least significant byte is stored at the lowest address) or Big-Endian (where the most significant byte is stored at the lowest address).

The following C program demonstrates this:

#include <stdio.h>

int main() {
    unsigned short val = 0x0001;
    char *ptr = (char *)&val;

    if (*ptr == 1) {
        printf("Host byte order is Little-Endian\n");
    } else {
        printf("Host byte order is Big-Endian\n");
    }
    return 0;
}

In this program:

• A 16-bit integer val is initialized to 1.
• A char pointer ptr is used to point to the first byte of the memory occupied by val.
• If the system is Little-Endian, the byte at the lowest address will be 0x01.
• If the system is Big-Endian, the byte at the lowest address will be 0x00.