TCP/IP : Transmission not working after string operations - c

Question

I'm trying to simulate a simple TCP connection between a client and a server, on the localhost. Things are working well without line 22 on "client.c" file, where I'm doing a string operation. With that line un-commented, the server apparently does not make the connection with the client.
I've been searching around for quite long, but I found nothing strictly related to this. It'd be great if I got some help. :)
Files:
client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <unistd.h>
#define BUFLEN 256
void error(char *msg)
{
perror(msg);
exit(0);
}
int main(int argc, char *argv[])
{
int sockfd, n;
//char filename[] = "file.txt"; // !!THE PROBLEM IS HERE!!
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[BUFLEN];
if (argc < 3) {
fprintf(stderr,"Usage %s server_address server_port\n", argv[0]);
exit(0);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(atoi(argv[2]));
inet_aton(argv[1], &serv_addr.sin_addr);
if (connect(sockfd,(struct sockaddr*) &serv_addr,sizeof(serv_addr)) < 0)
error("ERROR connecting");
while(1) {
memset(buffer, 0 , BUFLEN);
fgets(buffer, BUFLEN-1, stdin);
n = send(sockfd,buffer,strlen(buffer), 0);
if (n < 0)
error("ERROR writing to socket");
}
return 0;
}
server.c
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#define MAX_CLIENTS 5
#define BUFLEN 256
void error(char *msg)
{
perror(msg);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, portno, clilen;
char buffer[BUFLEN];
struct sockaddr_in serv_addr, cli_addr;
int n, i, j;
fd_set read_fds;
fd_set tmp_fds;
int fdmax;
if (argc < 2) {
fprintf(stderr,"Usage : %s port\n", argv[0]);
exit(1);
}
FD_ZERO(&read_fds);
FD_ZERO(&tmp_fds);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
portno = atoi(argv[1]);
memset((char *) &serv_addr, 0, sizeof(serv_addr));
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(struct sockaddr)) < 0)
error("ERROR on binding");
listen(sockfd, MAX_CLIENTS);
FD_SET(sockfd, &read_fds);
fdmax = sockfd;
// main loop
while (1) {
tmp_fds = read_fds;
if (select(fdmax + 1, &tmp_fds, NULL, NULL, NULL) == -1)
error("ERROR in select");
for(i = 0; i <= fdmax; i++) {
if (FD_ISSET(i, &tmp_fds)) {
if (i == sockfd) {
clilen = sizeof(cli_addr);
if ((newsockfd = accept(sockfd, (struct sockaddr *)&cli_addr, &clilen)) == -1) {
error("ERROR in accept");
}
else {
FD_SET(newsockfd, &read_fds);
if (newsockfd > fdmax) {
fdmax = newsockfd;
}
}
printf("New connection from IP %s, port %d, socket_client %d\n ", inet_ntoa(cli_addr.sin_addr), ntohs(cli_addr.sin_port), newsockfd);
}
else {
memset(buffer, 0, BUFLEN);
if ((n = recv(i, buffer, sizeof(buffer), 0)) <= 0) {
if (n == 0) {
printf("selectserver: socket %d hung up\n", i);
} else {
error("ERROR in recv");
}
close(i);
FD_CLR(i, &read_fds);
}
else { //recv > 0
printf ("I received from the client with socket %d, this message: %s\n", i, buffer);
}
}
}
}
}
close(sockfd);
return 0;
}
Compiling:
gcc client.c -o client
gcc server.c -o server
Running (in different terminals):
./server 9999
./client localhost 9999