Telnet client error in c++ - c++

Question

The telnet client code is :
enter code here
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <termios.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/telnet.h>
#define DO 0xfd
#define WONT 0xfc
#define WILL 0xfb
#define DONT 0xfe
#define CMD 0xff
#define CMD_ECHO 1
#define CMD_WINDOW_SIZE 31
void negotiate(int sock, unsigned char *buf, int len) {
int i;
if (buf[1] == DO && buf[2] == CMD_WINDOW_SIZE) {
unsigned char tmp1[10] = {255, 251, 31};
if (send(sock, tmp1, 3 , 0) < 0)
exit(1);
unsigned char tmp2[10] = {255, 250, 31, 0, 80, 0, 24, 255, 240};
if (send(sock, tmp2, 9, 0) < 0)
exit(1);
return;
}
for (i = 0; i < len; i++) {
if (buf[i] == DO)
buf[i] = WONT;
else if (buf[i] == WILL)
buf[i] = DO;
}
if (send(sock, buf, len , 0) < 0)
exit(1);
}
static struct termios tin;
static void terminal_set(void) {
// save terminal configuration
tcgetattr(STDIN_FILENO, &tin);
static struct termios tlocal;
memcpy(&tlocal, &tin, sizeof(tin));
cfmakeraw(&tlocal);
tcsetattr(STDIN_FILENO,TCSANOW,&tlocal);
}
static void terminal_reset(void) {
// restore terminal upon exit
tcsetattr(STDIN_FILENO,TCSANOW,&tin);
}
#define BUFLEN 20
int main(int argc , char *argv[]) {
int sock;
struct sockaddr_in server;
unsigned char buf[BUFLEN + 1];
int len;
int i;
if (argc < 2 || argc > 3) {
printf("Usage: %s address [port]\n", argv[0]);
return 1;
}
int port;
if (argc == 3)
port = atoi(argv[2]);
//Create socket
sock = socket(AF_INET , SOCK_STREAM , 0);
if (sock == -1) {
perror("Could not create socket. Error");
return 1;
}
server.sin_addr.s_addr = inet_addr(argv[1]);
server.sin_family = AF_INET;
server.sin_port = htons(port);
//Connect to remote server
if (connect(sock , (struct sockaddr*)&server , sizeof(server)) < 0) {
perror("connect failed. Error");
return 1;
}
puts("Connected...\n");
// set terminal
terminal_set();
atexit(terminal_reset);
struct timeval ts;
ts.tv_sec = 1; // 1 second
ts.tv_usec = 0;
while (1) {
// select setup
fd_set fds;
FD_ZERO(&fds);
if (sock != 0)
FD_SET(sock, &fds);
FD_SET(0, &fds);
// wait for data
int nready = select(sock + 1, &fds, (fd_set *) 0, (fd_set *) 0, &ts);
if (nready < 0) {
perror("select. Error");
return 1;
}
else if (nready == 0) {
ts.tv_sec = 1; // 1 second
ts.tv_usec = 0;
}
else if (sock != 0 && FD_ISSET(sock, &fds)) {
// start by reading a single byte
int rv;
if ((rv = recv(sock , buf , 1 , 0)) < 0)
return 1;
else if (rv == 0) {
printf("Connection closed by the remote end\n\r");
return 0;
}
if (buf[0] == CMD) {
// read 2 more bytes
len = recv(sock , buf + 1 , 2 , 0);
if (len < 0)
return 1;
else if (len == 0) {
printf("Connection closed by the remote end\n\r");
return 0;
}
negotiate(sock, buf, 3);
}
else {
len = 1;
buf[len] = '\0';
printf("%s", buf);
fflush(0);
}
}
else if (FD_ISSET(0, &fds)) {
buf[0] = getc(stdin); //fgets(buf, 1, stdin);
if (send(sock, buf, 1, 0) < 0)
return 1;
if (buf[0] == '\n') // with the terminal in raw mode we need to force a LF
putchar('\r');
}
}
close(sock);
return 0;
}
While the server code is :
enter code here
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <netdb.h>
int main(int argc , char *argv[])
{
int socket_desc , new_socket , c;
struct sockaddr_in server ,client;
char *message;
//create socket;
socket_desc = socket(AF_INET , SOCK_STREAM , 0);
if (socket_desc == -1)
{printf("Could not create socket");
}
//prepare sock addr structure
server.sin_family = AF_INET;
server.sin_addr.s_addr = INADDR_ANY;
server.sin_port = htons( 8888 );
//bind
if(bind(socket_desc, (struct sockaddr *)&server , sizeof(&server)) < 0)
{
printf("bind failed");
}
printf("Bind done");
//Listen
listen(socket_desc , 3);
//accept incoming connection
printf("Waiting for incoming connection ... ");
c =sizeof(struct sockaddr_in);
new_socket = accept(socket_desc, (struct sockaddr *)&client,sizeof(&client));
while(new_socket < 0);
{
puts("Connection Accepted");
message = "Hello Client ...Recieved your message \n";
write(new_socket , message , strlen(message));
}
if (new_socket < 0)
{
perror("accept failed");
return 1;
}
return 0;
}
On executing the programs from command line :
./server 8000
./telnet_client 127.0.0.1 8000
The telnet client gives the error "Connect failed.Error:Connection refused"
Kindly help how to successfully execute the program

Answer 1

You are listening on 8888 port but trying to connect to 8000. Although you are passing 8000 parameter to server program you don't do anything with it. To correct this don't hard code
server.sin_port = htons( 8888 );
but instead process parameters passed to the program
if ( argc != 2)
err_quit("usage: server <port>"); // or maybe use some default
//...
server.sin_port = htons( atoi( argv[1]) );

Answer 2

in the server
int port = 8888;
...
if (argc < 1 || argc > 2) {
printf("Usage: %s [port(default=8888)] \n", argv[0]);
return 1;
}
port = (argc == 2) ? atoi(argv[1]);
...
server.sin_port = htons(port);
...