Linker error

#include <stdio.h>
#include <sys/types.h>
#include <winsock2.h>

#define BUFFER_SIZE 1024

int main()
{
 SOCKADDR_IN addr;
 
 struct sockaddr_in 
 {
 short sin_family;
 unsigned short sin_port;
 struct in_addr sin_addr;
 char sin_zero[0];
 };
 
 struct sockaddr_in srv;
 int sock, c, bytes;
 char buffer[BUFFER_SIZE];
 
 sock = socket(AF_INET, SOCK_STREAM, 0);
 if (sock==-1)
 {
 perror("Konnte keinen Socket erstellen\n");
 exit(0);
 }
 
 srv.sin_addr.s_addr = inet_addr("127.0.0.1");
 srv.sin_port = 70;
 srv.sin_family = AF_INET;
 
 c = connect(sock, (SOCKADDR*)&srv, sizeof(srv));
 
 if (c==-1)
 {
 perror("Konnte keine Verbindung zum Server herstellen.\n");
 exit(0);
 }
 
 bytes = recv(sock, buffer, sizeof(buffer)-1, 0);
 if(bytes=-1)
 {
 perror("Konnte vom Socket nicht lesen.\n");
 }
 
 // buffer[bytes] = "\0";
 
 printf("\nAusgabe: %s\n\n", buffer);
 
 return 0;
}