socket.h

/**
// SAMPLE
int main(void) {
    SocketInit();
    struct sockaddr_in addr;
    SocketResolve(&addr, "localhost", 5432);
    Socket sock = SocketUDP(false);
    // connected udp can use send/recv instead of sendto/recvfrom
    connect(sock, (const struct sockaddr *) &addr, sizeof(addr));
    const char *data = "hello world";
    send(sock, data, strlen(data), 0);
    struct timeval timeout = {0};
    timeout.tv_sec = 4;
    if(SocketReadable(sock, &timeout) > 0) {
        uint8_t buf[8*1024];
        int received = recv(sock, buf, 8*1024, 0);
        if(received > 0) {
            printf("%.*s\n", received, buf);
        }
    }
    SocketClose(sock);
    SocketQuit();
    return 0;
}
*/

#include <netinet/in.h>
#ifdef _WIN32
#include <Ws2tcpip.h>
#include <winsock2.h>
typedef SOCKET Socket;
#else
#include <arpa/inet.h>
#include <fcntl.h>
#include <netdb.h>
#include <sys/socket.h>
#include <unistd.h>
typedef int Socket;
#endif

// returns 0 on success
static int SocketInit(void) {
#ifdef _WIN32
  WSADATA wsa_data;
  return WSAStartup(MAKEWORD(1, 1), &wsa_data);
#else
  return 0;
#endif
}

// returns 0 on success
static int SocketQuit(void) {
#ifdef _WIN32
  return WSACleanup();
#else
  return 0;
#endif
}

// returns 0 on success
static int SocketResolve(struct sockaddr_in *addr, char *host, uint16_t port) {
  struct hostent *h = gethostbyname(host);
  if (h == NULL) {
    return 1;
  }
  addr->sin_family = h->h_addrtype;
  memcpy((char *)&(addr->sin_addr), h->h_addr, h->h_length);
  addr->sin_port = htons(port);
  return 0;
}

// SocketBind(sock, INADDR_ANY, port) to receive from everybody on port
// returns 0 on success
static int SocketBind(Socket sock, unsigned long address, uint16_t port) {
  struct sockaddr_in server = {0};
  server.sin_family = AF_INET;
  server.sin_addr.s_addr = htonl(address);
  server.sin_port = htons(port);
  return bind(sock, (struct sockaddr *)&server, sizeof(server));
}

// returns positive on success
static Socket SocketUDP(bool blocking) {
  Socket s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if (!blocking) {
    fcntl(s, F_SETFL, O_NONBLOCK);
  }
  return s;
}

// returns positive on success
static Socket SocketTCP(bool blocking) {
  Socket s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (!blocking) {
    fcntl(s, F_SETFL, O_NONBLOCK);
  }
  return s;
}

// returns 0 on timeout, positive value on success
static int SocketReadable(Socket sock, struct timeval *timeout) {
  fd_set socks;
  FD_ZERO(&socks);
  FD_SET(sock, &socks);
  return select(sock + 1, &socks, NULL, NULL, timeout);
}

static void SocketClose(Socket sock) {
#ifdef _WIN32
  closesocket(sock);
#else
  close(sock);
#endif
}