TCP Server in C

#include <stdio.h> 
#include <sys/types.h> 
#include <sys/socket.h> 
#include <netinet/in.h> 

void error(char *msg){    
	perror(msg);    
	exit(0);
}

int main(int argc, char *argv[]){    
	int sockfd, newsockfd, portno, clilen; 
	char buffer[256]; 
	struct sockaddr_in serv_addr, cli_addr; 
	int n; 
	
	if (argc < 2) { 
		fprintf(stderr,"ERROR, no port provided\n"); 
		exit(1); 
	} 
	
	sockfd = socket(AF_INET, SOCK_STREAM, 0); 
	
	if (sockfd < 0) 
		error("ERROR opening socket"); 
	
	bzero((char *) &serv_addr, sizeof(serv_addr)); 
	portno = atoi(argv[1]); 
	serv_addr.sin_family = AF_INET; 
	serv_addr.sin_addr.s_addr = INADDR_ANY; 
	serv_addr.sin_port = htons(portno); 
	
	if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) 		
		error("ERROR on binding"); 

	listen(sockfd,5); 
	clilen = sizeof(cli_addr); 
	newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen); 
	
	if (newsockfd < 0) 
		error("ERROR on accept"); 
	
	bzero(buffer,256); 
	n = recv(newsockfd,buffer,255,0); 
	
	if (n < 0) 
		error("ERROR reading from socket"); 
	
	printf("Here is the message: %s\n",buffer); 
	n = send(newsockfd,"I got your message",18,0); 
	
	if (n < 0) 
		error("ERROR writing to socket");
	
	close(newsockfd);
	close(sockfd); 
	return 0; 
} 


==================================================================================================
TCP Client in C

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h> 

void error(char *msg){    
	perror(msg);    
	exit(0);
}

int main(int argc, char *argv[]){    
	int sockfd, portno, n;    
	struct sockaddr_in serv_addr;    
	struct hostent *server;    
	char buffer[256];  
  
	if (argc < 3) {
	  	fprintf(stderr,"usage %s hostname port\n", argv[0]); 
		exit(0);    
	}    
	portno = atoi(argv[2]);    

	sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);    
	
	if (sockfd < 0)         
		error("ERROR opening socket");    
	
	server = gethostbyname(argv[1]);    
	
	if (server == NULL) {  
		fprintf(stderr,"ERROR, no such host\n"); 
		exit(0);    
	}    	
	
	bzero((char *) &serv_addr, sizeof(serv_addr));    
	serv_addr.sin_family = AF_INET;    
	bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr
		, server->h_length);    
	serv_addr.sin_port = htons(portno);    

	if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0)  
		error("ERROR connecting");   
 
	printf("Please enter the message: ");    
	bzero(buffer,256);    
	fgets(buffer,255,stdin);    
	n = send(sockfd,buffer,strlen(buffer),0);    

	if (n < 0)          
		error("ERROR writing to socket");    
	bzero(buffer,256);    
	n = recv(sockfd,buffer,255,0);    
	if (n < 0)
	          error("ERROR reading from socket");    
	printf("%s\n",buffer);  
	close(sockfd);  
	return 0;
} 



===========================================================================================================


UDP Client in C

	sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
	len = sizeof(struct sockaddr_in);

	while (1) { 
		/* write */
		n = sendto(sock,“Got your message\n",17, 0,(struct sockaddr *) &server, len); 
		f (n < 0) error("sendto"); 

		/* read */
		n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from, len); 		
		if (n < 0) error("recvfrom");
	} 



UDP Server in C

	sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

	len = sizeof(struct sockaddr_in);
	while (1) { 
		/* read */
		n = recvfrom(sock,buf,1024,0,(struct sockaddr *)&from, len); 		
		if (n < 0) error("recvfrom");
	
		/* write */
		n = sendto(sock,"Got your message\n",17, 0,(struct sockaddr *)&from, len); 
		f (n < 0) error("sendto"); 
	}