/* Start of the Program SERVERTCP.C */
/* SIVA SANTOSH VARMA ALLURI, K00351411 , Operating System Sec 003 */
/* This is an server side program for TCP based echo server using socket programming in UNIX using C programming. */
 
/* Include the necessary header files */
 
#include<stdio.h>			/* IO stream Interface */
#include<stdlib.h>			/* Standard General Utilities Library */
#include<unistd.h>			/*  misc. UNIX functions      */
#include<sys/socket.h> 		/*  socket definitions, pointer to socket address  */
#include<sys/types.h> 		/*  data type of socket address structure */
#include<netinet/in.h>		/*  for IPv4 socket address */
#include<netdb.h>  			/* structure for network host entry */
#include<strings.h>			/* String manipulation operations */
#include<fcntl.h>			/* file control options */
#include<arpa/inet.h>		/* This is used to convert internet addresses between ASCII */  
							/* strings and network byte ordered binary values */
 
 
 
 
int main(int asrgc,char*argv[]) 		/* start of main function */
 
{ 
 
int bd,sd,ad;  			/* bd is local protocol address to the socket */
						/* sd is Internet socket address structure */
						/* ad is accepted address */
 
char buff[1024]; 			/* Buffer size */
 
struct sockaddr_in cliaddr,servaddr; 	/* Create a socket using socket function with */
				/* family AF_INET, type as SOCK_STREAM */
socklen_t clilen; 			/* Size of Host address */
clilen=sizeof(cliaddr); 		/* Size of Client address */
 
bzero(&servaddr,sizeof(servaddr));  	/* Initialize server address to 0 using the bzero function.*
 
 
/* Socket address structure*/ 
 
/* Assign the sin_family to AF_INET, sin_addr to INADDR_ANY, sin_port to a dynamically 
assigned port number. */
 
	servaddr.sin_family=AF_INET; 
	servaddr.sin_addr.s_addr=htonl(INADDR_ANY); 
	servaddr.sin_port=htons(1999); 
 
/*TCP socket is created, an Internet socket address structure is filled with wildcard address 
& server’s well known port*/ 
 
	sd=socket(AF_INET,SOCK_STREAM,0); 
 
 /*Bind function assigns a local protocol address to the socket*/ 
 
	bd=bind(sd,(struct sockaddr*)&servaddr,sizeof(servaddr)); 
 
/*Listen function specifies the maximum number of connections that kernel should queue 
for this socket*/ 
 
	listen(sd,5); 
	printf("SIVA SANTOSH VARMA ALLURI, OS, Sec 003  Server is running….\n"); 
 
 /*The server to return the next completed connection from the front 
of the  completed connection Queue calls it*/ 
 
/* Accept connection request from the client using accept function.*/
 
	ad=accept(sd,(struct sockaddr*)&cliaddr,&clilen); 
 
/* Within an infinite loop, using the recv function receive message from the client and print it 
on the console */
 
	while(1) 
		{ 
		bzero(&buff,sizeof(buff)); 
 
 		recv(ad,buff,sizeof(buff),0); 	/*Receiving the request message from the client*/
 
		printf(" Message received by SIVA SANTOSH VARMA ALLURI, OS , Sec 003”); 
		printf("Operating System Sec 003 is %s\n",buff);
 
					/* Print Acknowledgement of received message */
} 					/* End of Program */
 
}
 

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