server.c

#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdlib.h>

int main()
{
    int ser_fd,cln_fd;
    int ser_len , cln_len;
    struct sockaddr_in ser_addr;
    struct sockaddr_in  cli_addr;

    ser_fd=socket(AF_INET, SOCK_STREAM, 0);

    ser_addr.sin_family= AF_INET;
    ser_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    ser_addr.sin_port=9734;
    ser_len = sizeof(ser_addr);

    bind(ser_fd, (struct sockaddr *)&ser_addr, ser_len);

    listen(ser_fd,5);

    while(1)
    {
        char ch;
        printf("server waiting\n");
        cln_len = sizeof(cli_addr);

        cln_fd = accept(ser_fd, (struct sockaddr *)&cli_addr, &cln_len);

        read(cln_fd, &ch ,1);
        ch++;
        write(cln_fd, &ch,1);
        close(cln_fd);

    }

}