Trigonometric Calculator using TCP Socket

Socket :

A socket is one endpoint of a two-way communication link between two programs running on the network. A socket is bound to a port number so that the TCP layer can identify the application that data is destined to be sent to. An endpoint is a combination of an IP address and a port number.

Program :

Server Side :

#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<netinet/in.h> 
#include <unistd.h>
#include<string.h> 
#include <arpa/inet.h>
#include<math.h>
#define PI 3.14159265
void main()
{
int b,sockfd,connfd,sin_size,l,n,len;
char op;
double angle1;

double result,val;

if((sockfd=socket(AF_INET,SOCK_STREAM,0))>0)
printf("socket created sucessfully\n");  //socket creation
//printf("%d\n", sockfd);                 //on success 0 otherwise -1

struct sockaddr_in servaddr;              
struct sockaddr_in clientaddr;

servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=6666;

if((bind(sockfd, (struct sockaddr *)&servaddr,sizeof(servaddr)))==0)
printf("bind sucessful\n");   //bind() assigns the
     //  address  specified  by  addr  to  the  socket  referred  to by the file
      // descriptor sockfd.  addrlen  specifies  the  size,  in  bytes,  of  the
     //  address structure pointed to by addr.  Traditionally, this operation is
      // called “assigning a name to a socket”.

//printf("%d\n",b);

if((listen(sockfd,5))==0) //listen for connections on a socket
printf("listen sucessful\n");
//printf("%d\n",l);

sin_size = sizeof(clientaddr);
if((connfd=accept(sockfd,(struct sockaddr *)&clientaddr,&sin_size))>0);
printf("accept sucessful\n");
val = PI / 180;
read(connfd, &op,1);
//printf("\n op=%d",op);

read(connfd, &angle1, sizeof(angle1));
//printf("\n angle is=%lf \n",angle1);

switch(op) {
        case '1': 
			
			result=sin(angle1*val);
         printf("sin(%lf)=%lf ",angle1,result);
         break;
        case '2':result=cos(angle1*val);
         printf("cos(%lf) =%lf ",angle1,result);
                break;
        case '3':result=tan(angle1*val);
         printf("tan(%lf) = %lf",angle1,result);
                break;
        
     default: 
                printf("ERROR: Unsupported Operation");
    }
  
write(connfd,&result,sizeof(result));

close(connfd);   
close(sockfd);
}

Client Side :

#include<sys/types.h>
#include<sys/socket.h>
#include<stdio.h>
#include<netinet/in.h> 
#include <unistd.h>
#include<string.h> 
#include<strings.h>
#include <arpa/inet.h>
#include<math.h>
//#define buffsize  150
void main()
{
int b,sockfd,sin_size,con,n,len;
//char buff[256];
double angle,result;
char op;

if((sockfd=socket(AF_INET,SOCK_STREAM,0))>0)
printf("socket created sucessfully\n");
//printf("%d\n", sockfd);
struct sockaddr_in servaddr;

servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=6666;

sin_size = sizeof(servaddr);
if((con=connect(sockfd,(struct sockaddr *) &servaddr, sin_size))==0); //initiate a connection on a socket
printf("connect sucessful\n");
printf("Enter operation:\n 1:sin \n 2:cos\n 3:tan \n ");
scanf("%c",&op);
printf("Enter angle in degree:");
scanf("%lf",&angle);

write(sockfd,&op,1);

write(sockfd,&angle,sizeof(angle));

read(sockfd,&result,sizeof(result)); 
printf("\n Operation result from server=%lf\n",result);  
close(sockfd);
}