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#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "micetrap.h"
#define BUFSIZE 1024
void error(char *msg) {
perror(msg);
exit(1);
}
int main(int argc, char **argv) {
int parentfd; /* parent socket */
int childfd; /* child socket */
int portno; /* port to listen on */
int clientlen; /* byte size of client's address */
struct sockaddr_in serveraddr; /* server's addr */
struct sockaddr_in clientaddr; /* client addr */
struct hostent *hostp; /* client host info */
char buf[BUFSIZE]; /* message buffer */
char *hostaddrp; /* dotted decimal host addr string */
int optval; /* flag value for setsockopt */
int n; /* message byte size */
/*
* check command line arguments
*/
if (argc != 2) {
fprintf(stderr, "usage: %s <port>\n", argv[0]);
exit(1);
}
portno = atoi(argv[1]);
/*
* socket: create the parent socket
*/
parentfd = socket(AF_INET, SOCK_STREAM, 0);
if (parentfd < 0)
error("ERROR opening socket");
/* setsockopt: Handy debugging trick that lets
* us rerun the server immediately after we kill it;
* otherwise we have to wait about 20 secs.
* Eliminates "ERROR on binding: Address already in use" error.
*/
optval = 1;
setsockopt(parentfd, SOL_SOCKET, SO_REUSEADDR,
(const void *)&optval , sizeof(int));
/*
* build the server's Internet address
*/
bzero((char *) &serveraddr, sizeof(serveraddr));
/* this is an Internet address */
serveraddr.sin_family = AF_INET;
/* let the system figure out our IP address */
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
/* this is the port we will listen on */
serveraddr.sin_port = htons((unsigned short)portno);
/*
* bind: associate the parent socket with a port
*/
if (bind(parentfd, (struct sockaddr *) &serveraddr,
sizeof(serveraddr)) < 0)
error("ERROR on binding");
/*
* listen: make this socket ready to accept connection requests
*/
if (listen(parentfd, 5) < 0) /* allow 5 requests to queue up */
error("ERROR on listen");
/*
* main loop: wait for a connection request, echo input line,
* then close connection.
*/
clientlen = sizeof(clientaddr);
while (1) {
/*
* accept: wait for a connection request
*/
childfd = accept(parentfd, (struct sockaddr *) &clientaddr, &clientlen);
if (childfd < 0)
error("ERROR on accept");
/*
* gethostbyaddr: determine who sent the message
*/
hostp = gethostbyaddr((const char *)&clientaddr.sin_addr.s_addr,
sizeof(clientaddr.sin_addr.s_addr), AF_INET);
if (hostp == NULL)
error("ERROR on gethostbyaddr");
hostaddrp = inet_ntoa(clientaddr.sin_addr);
if (hostaddrp == NULL)
error("ERROR on inet_ntoa\n");
printf("server established connection with %s (%s)\n",
hostp->h_name, hostaddrp);
/*
* read: read input string from the client
*/
bzero(buf, BUFSIZE);
n = read(childfd, buf, BUFSIZE);
if (n < 0)
error("ERROR reading from socket");
printf("server received %d bytes: %s", n, buf);
/*
* write: echo the input string back to the client
*/
n = write(childfd, buf, strlen(buf));
if (n < 0)
error("ERROR writing to socket");
close(childfd);
}
}
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