Socket Programming in C, TCP over a network (2 systems)

    #include"stdio.h"
    #include"stdlib.h"
    #include"sys/types.h"
    #include"sys/socket.h"
    #include"string.h"
    #include"netinet/in.h"

    #define PORT 4444
    #define BUF_SIZE 2000

    void main() {
     struct sockaddr_in addr, cl_addr;
     int sockfd, len, ret, newsockfd;
     char buffer[BUF_SIZE];
     
     sockfd = socket(AF_INET, SOCK_STREAM, 0);
     if (sockfd < 0) {
      printf("Error creating socket!\n");
      exit(1);
     }
     printf("Socket created...\n");
     
     memset(&addr, 0, sizeof(addr));
     addr.sin_family = AF_INET;
     addr.sin_addr.s_addr = INADDR_ANY;
     addr.sin_port = PORT;
     
     ret = bind(sockfd, (struct sockaddr *) &addr, sizeof(addr));
     if (ret < 0) {
      printf("Error binding!\n");
      exit(1);
     }
     printf("Binding done...\n");

     printf("Waiting for a connection...\n");
     listen(sockfd, 5);

     len = sizeof(cl_addr);
     newsockfd = accept(sockfd, (struct sockaddr *) &cl_addr, &len);
     if (newsockfd < 0) {
      printf("Error accepting connection!\n");
      exit(1);
     }
     printf("Connection accepted...\n"); 

     memset(buffer, 0, BUF_SIZE);
     ret = recv(newsockfd, buffer, BUF_SIZE, 0);
     if(ret < 0) {
      printf("Error receiving data!\n");  
      exit(1);
     }
     printf("Received data: %s\n", buffer); 

     ret = send(newsockfd, buffer, strlen(buffer), 0);  
     if (ret < 0) {  
      printf("Error sending data!\n");  
      exit(1);  
     }  
     printf("Sent data: %s\n", buffer);
     close(sockfd);
     close(newsockfd);
    }

     
    #include"stdio.h"  
    #include"stdlib.h"  
    #include"sys/types.h"  
    #include"sys/socket.h"  
    #include"string.h"  
    #include"netinet/in.h"  
    #include"netdb.h"
      
    #define PORT 4444 
    #define BUF_SIZE 2000 
      
    int main(int argc, char**argv) {
     struct sockaddr_in addr, cl_addr;  
     int sockfd, ret;  
     char buffer[BUF_SIZE];  
     struct hostent * server;
     char * serverAddr;

     if (argc < 2) {
      printf("usage: client < ip address >\n");
      exit(1);  
     }

     serverAddr = argv[1];

     sockfd = socket(AF_INET, SOCK_STREAM, 0);  
     if (sockfd < 0) {  
      printf("Error creating socket!\n");  
      exit(1);  
     }  
     printf("Socket created...\n");   

     memset(&addr, 0, sizeof(addr));  
     addr.sin_family = AF_INET;  
     addr.sin_addr.s_addr = inet_addr(serverAddr);
     addr.sin_port = PORT;     

     ret = connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));  
     if (ret < 0) {  
      printf("Error connecting to the server!\n");  
      exit(1);  
     }  
     printf("Connected to the server...\n");  

     memset(buffer, 0, BUF_SIZE);
     printf("Enter your message: ");
     scanf("%s", buffer);
     ret = send(sockfd, buffer, strlen(buffer), 0);  
     if (ret < 0) {  
      printf("Error sending data!\n");  
      exit(1);  
     }  
     printf("Sent data: %s\n", buffer);  

     memset(buffer, 0, BUF_SIZE);  
     ret = recv(sockfd, buffer, BUF_SIZE, 0);  
     if(ret < 0) {  
      printf("Error receiving data!\n");    
      exit(1);  
     }  
     printf("Received data: %s\n", buffer); 

     return 0;
    }