simple echo server demonstration

server.c

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

void dostuff(int);
void error(char *msg)
{
		perror(msg);
		exit(1);
}

int main(int argc, char *argv[])
{
		int sockfd, newsockfd, portno, clilen, pid, optval;
		struct sockaddr_in serv_addr, cli_addr;

		if(argc < 2) {
				fprintf(stderr, "Error, no port provided\n");
				exit(1);
		}

		sockfd = socket(AF_INET, SOCK_STREAM, 0);
		optval = 1;
		setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval));
		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_port = htons(portno);
		serv_addr.sin_addr.s_addr = INADDR_ANY;
		if (bind(sockfd, (struct sockaddr *) &serv_addr,
				 sizeof(serv_addr)) < 0)
				error("Error on binding");

		listen(sockfd, 5);

		clilen = sizeof(cli_addr);

		while(1) {
				newsockfd = accept(sockfd,
								   (struct sockaddr *) &cli_addr, &clilen);
				if (newsockfd < 0)
						error("Error on accept");

				pid = fork();
				if (pid < 0)
						error("Error on fork");

				if (pid == 0) {
						close(sockfd);
						dostuff(newsockfd);
						exit(0);
				}
				else
						close(newsockfd);

		}
		return 0;
}

void dostuff(int newsockfd) {
		int n;
		char buffer[256];
		char exit[] = "exit";
		
		while(1) {
				bzero(buffer, 256);
				n = read(newsockfd, buffer, 255);
				if (n < 0)
						error("Error reading from socket");

				n = strcmp(buffer, exit);
				if (n == 0)
						break;

				printf("Here is the message: %s\n", buffer);

				n = write(newsockfd, "I got your message\n", 18);
				if (n < 0)
						error("Error writing to socket");
		}

}