C++ Socket libraries are not being identified by the compiler

Question

I am trying to to learn how to stream image frames via UDP in C++ and I was following this tutorial for the server part to receive my frames, this tutorial clearly uses code from question stackoverflow question. However, after following up both sources, whenever I attempt to load my libraries in geany/c++:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h> 
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <iostream>


using namespace std;
using namespace cv;

#define width 320
#define height 240
int imgSize;
int bytes=0;
bool running = true;
char key;
const int ah = 230400;
    
int main(int argc, char * argv[]) {
    
    SOCKET server;
    SOCKADDR_IN addr;
    server = socket(AF_INET, SOCK_STREAM, 0);
    addr.sin_addr.s_addr = inet_addr("127.0.0.1");
    addr.sin_family = AF_INET;
    addr.sin_port = htons(9999);
    connect(server, (SOCKADDR *)&addr, sizeof(addr));
    return 0;
}

This gives me the following errors:

/home/pi/Documentos/cam.cpp: In function ‘int main(int, char**)’:
/home/pi/Documentos/cam.cpp:27:2: error: ‘SOCKET’ was not declared in this scope
   27 |  SOCKET server;
      |  ^~~~~~
/home/pi/Documentos/cam.cpp:28:2: error: ‘SOCKADDR_IN’ was not declared in this scope
   28 |  SOCKADDR_IN addr;
      |  ^~~~~~~~~~~
/home/pi/Documentos/cam.cpp:29:2: error: ‘server’ was not declared in this scope; did you mean ‘servent’?
   29 |  server = socket(AF_INET, SOCK_STREAM, 0);
      |  ^~~~~~
      |  servent
/home/pi/Documentos/cam.cpp:30:2: error: ‘addr’ was not declared in this scope
   30 |  addr.sin_addr.s_addr = inet_addr("127.0.0.1");
      |  ^~~~
/home/pi/Documentos/cam.cpp:30:25: error: ‘inet_addr’ was not declared in this scope; did you mean ‘in6_addr’?
   30 |  addr.sin_addr.s_addr = inet_addr("127.0.0.1");
      |                         ^~~~~~~~~
      |                         in6_addr
/home/pi/Documentos/cam.cpp:33:19: error: ‘SOCKADDR’ was not declared in this scope
   33 |  connect(server, (SOCKADDR *)&addr, sizeof(addr));
      |                   ^~~~~~~~
/home/pi/Documentos/cam.cpp:33:29: error: expected primary-expression before ‘)’ token
   33 |  connect(server, (SOCKADDR *)&addr, sizeof(addr));

Forgive my ignorance, I'd like to know what is the right way to create a UDP socket for a specific IP/Port

I believe that's based on the Windows API, so you'll have to port it to normal BSD Sockets API first. — Ulrich Eckhardt, Jul 02 '22 at 07:17

Afshin · Accepted Answer · 2022-07-02T07:24:44.703

You are using SOCKET or SOCKADDR_IN which is Microsoft dedicated but I see Linux headers.

You need to select what you want to do:

You need code only for Windows.
You need code only for Linux.
You need a cross-platform code.

Your approach somehow differs based on what you want to do.

If your code is supposed to work on Windows only, replace:

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

with:

#include <windows.h>
#include <winsock2.h>

and also add WSAStartup() and WSACleanup() to your code (I'm almost sure you will miss this part if you are socket programming on Windows). You also need to link your code with Ws2_32.lib.

If you are coding for Linux, replace SOCKET with int, SOCKADDR_IN with sockaddr_in, and SOCKADDR with sockaddr and try again.

@xnok then go with linux one. – Afshin Jul 02 '22 at 07:32 — Afshin, Jul 02 '22 at 07:32

score 0 · Answer 2 · answered Jul 02 '22 at 07:38

That's WinSock code. And techniques and functions available there aren't 100% matching between POSIX and WinSock. I wouldn't recommend to define own version of Windows types, that would be misleading and hard to see which part of code were refactored. Rather go with something like:

#ifdef WINDOWS_PC /** some predefined  macro */
typedef SOCKET socket_t;
#else
#  ifdef POSIX /** some predefined  macro */
typedef int    socket_t;
#  endif
#endif

POSIX-compatible types relevant to SOCKADDR_IN and SOCKADDR were sockaddr_in and sockaddr, they were to be available in WinSock2.

WinSock functionality uses a special function for getting error codes instead of errno which is used in POSIX. There is no ioctl in Winsock function, instead there is not quite same ioctlsocket, Windows closesocket would be replaced just by close because POSIX socket is either a file(stream) or block device, read/write can be used on it.

C++ Socket libraries are not being identified by the compiler

2 Answers2