UNIX for Dummies Questions & Answers

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/time.h>
#include <signal.h>
#include <fcntl.h>
#define SIZE 100
//signal handler for sigpipe signal

void sig_handler(int signo)
{
        if(signo == SIGPIPE)
        {
                printf("Signal Received\n");
        }
}
int main()
{
        int server_sockfd,client_sockfd;
        int sfd=0;
        int fd;
        int server_len,client_len;
        int select_retval;
        char buf[SIZE];
        struct sockaddr_un server_address;
        struct sockaddr_un client_address;
        struct timeval timebuf;
        fd_set read_fds,set;
        //Register the SIGPIPE signal
        signal(SIGPIPE,sig_handler);
        //Remove the old socket
        unlink("Server_Multi_TCP");
        //creating the socket
        if((server_sockfd = socket(AF_UNIX,SOCK_STREAM,0))==-1)
        {
                perror("socket error");
                exit(0);
        }
        //Naming the socket
        server_address.sun_family = AF_UNIX;
        strcpy(server_address.sun_path,"Server_Multi_TCP");
        server_len = sizeof(server_address);
        if((bind (server_sockfd,(struct sockaddr *)&server_address,server_len))==-1)
        {
                perror("bind error");
                exit(0);
        }
        //create a connection queue and waiting for clients
        if(listen(server_sockfd,5)==-1)
        {
                perror("listen error");
                exit(0);
        }
        if(server_sockfd > sfd)
                sfd = server_sockfd;
        FD_ZERO(&set);
        FD_SET(server_sockfd,&set);
        //select time value
        struct timeval tv;
        /*tv.tv_sec = 10; //number of seconds to wait
        tv.tv_usec = 500000; //number of micro seconds to wait*/
        while(1)
        {
                read_fds = set;
                printf("Server is Waiting\n");
                //Accept a connection
                if ((select_retval = select(sfd+1,&read_fds,NULL,NULL,NULL))==-1)
                {
                        perror("select error");
                        exit(0);
                }
                for (fd = 0;fd<=sfd;fd++)
                {
                        if(FD_ISSET(fd,&read_fds))
                        {
                                if(fd==server_sockfd)
                                {
                                        client_len = sizeof(client_address);
                                        if((client_sockfd = accept(server_sockfd,NULL,0))==-1)
                                        {
                                                perror("accept error");
                                                exit(0);
                                        }
                                        write(client_sockfd,"Server got your request\n",24);
                                        FD_SET(client_sockfd,&set);
                                        if(client_sockfd > sfd)
                                                sfd = client_sockfd;
                                }
                                else
                                {
                                        int nread;
                                        nread = read(fd,buf,sizeof(buf));
                                        buf[nread] = '\0';
                                        if(nread == 0)
                                        {
                                                FD_CLR(fd,&set);
                                                if(fd == sfd)
                                                        sfd--;
                                                printf("Client %d is closed\n",sfd);
                                                close(fd);
                                        }
                                        else
                                        {
                                                printf("Server got message %s from client\n",buf,sfd);
                                                write(fd,"server listening\n",17);
                                        }
                                }
                        }
                }
        }
        close(server_sockfd);
}

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <signal.h>
void sig_handler(int);
int main()
{
        int sockfd;
        int len;
        struct sockaddr_un address;
        int result;
        char ch[100] ;
        char ch1[100];
        int n;
        //registering the SIGPIPE signal
        signal(13,sig_handler);
        //creating socket for client

        sockfd = socket(AF_UNIX,SOCK_STREAM,0);
        //name the socket agreed with the server
        address.sun_family = AF_UNIX;
        strcpy(address.sun_path, "server_socket");
        len = sizeof(address);
        //now connect our socket to the server's socket
        result = connect(sockfd,(struct sockaddr *)&address,len);
        if (result == -1)
        {
                perror("oops:client1");
                exit(1);
        }
        //now read and write via socket
        while(1)
        {
                printf("Enter the data\n");
                n=read(0,ch,100);
                //      printf("read return:%d\n",n);
                char close[100]= "client closed";
                if (n==0)
                {
                        write(sockfd,close,sizeof(close));
                        exit(0);
                }
                n=write(sockfd,ch,n);
                //      printf("write return:%d\n",n);
                //      sleep(3);
        //      printf("Reply from server:");
                n=read(sockfd,ch1,100);
                if (n==0)
                {
                        printf("Sorry! Server is closed\n");
                        printf("Bye!Bye!\n");
                        exit(0);
                }
                write(1,"Message from server:\n",21);
                write(1,ch1,n);
                //printf("%c",ch1);
        }
        close(sockfd);
        exit(0);
}
void sig_handler(int signo)
{
        if (signo == SIGPIPE)
        {
                printf("SIGPIPE SIGNAL RECEIVED\n");
                exit(0);
        }
}