socket connection failure - c

Question

I am beginner in socket programming and reading Linux Network Programming book. I decided to implement client-server connection as shown in the book. Server program is run on Ubuntu 14.04 machine and client code is run from Mac machine. The server code is the following
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <string.h>
const char message[] = "hello, world\n";
int main()
{
int sock = 0;
int port = 0;
sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock == -1)
fprintf(stderr, "failed\n");
else
printf("connection is establisshed\n");
struct sockaddr_in server;
server.sin_family = AF_INET;
server.sin_addr.s_addr = htonl(INADDR_ANY );
server.sin_port = 3500;
int status = bind(sock, (struct sockaddr*) &server, sizeof(server));
if (status == 0)
printf("connection completed\n");
else
printf("problem is encountered\n");
status = listen(sock, 5);
if (status == 0)
printf("app is ready to work\n");
else
{
printf("connection is failed\n");
return 0;
}
while (1)
{
struct sockaddr_in client = { 0 };
int sclient = 0;
int len = sizeof(client);
int childSocket = accept(sock, (struct sockaddr*) &client, &len);
if (childSocket == -1)
{
printf("cannot accept connection\n");
close(sock);
break;
}
write(childSocket, message, strlen(message));
close(childSocket);
}
return 0;
}
As for client side i wrote the following code
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
int main(int argc, char* argv[])
{
int sock = 0;
int port = 0;
struct sockaddr_in servaddr;
sock = socket(AF_INET, SOCK_STREAM, 0);
int status = 0;
char buffer[256] = "";
if (sock == -1)
{
printf("could not establish connection\n");
exit(1);
}
port = 3500;
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = inet_addr(argv[1]);
servaddr.sin_port = htons(port);
status = connect(sock, (struct sockaddr*) &servaddr, sizeof(servaddr));
if (status == 0)
printf("connection is established successfully\n");
else
{
printf("could not run the app\n");
exit(1);
}
status = read(sock, buffer, sizeof(buffer));
if (status > 0)
printf("%d: %s", status, buffer);
close(sock);
return 0;
}
To get IP address of client machine I run ifconfig from terminal an get inet_addr 192.168.1.165 value. Now when I pass that address string as command line argument I get message that app is not running message. There is problem with address that I got, as I understand. So what is the problem?
Thanks in advance

Answer 1

Most probably the server does not listen on the port you are assuming, that is 3500.
To fix this, change this line:
server.sin_port=3500
to be
server.sin_port = htons(3500);
(To monitor which process is listing on which address:port you might like to use the netstat command line tool. In your case probably using the options -a -p -n )
Also on recent systems accept() expects a pointer to socklen_t as last parameter, so change this
int len=sizeof(client);
to be
socklen_t len = sizeof client; /* sizeof is an operator, not a function¨*/