void sendudptolocal(uchar *buf, int len)
{
    int sock;
    struct sockaddr_in addr;
 
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
        return;
 
    addr.sin_family = AF_INET;
    addr.sin_port = htons(scl.serverport+2);
    addr.sin_addr.s_addr = INADDR_ANY;
 
    sendto(sock, buf, len, 0, (struct sockaddr*)&addr, sizeof(addr));
 
    close(sock);
}

1. 59068 362.790364663 127.0.0.1 127.0.0.1 UDP 66 35902 → 28765  Len=22

void sendudptolocal(uchar *buf, int len)
{
    static int sock = -1;
    struct sockaddr_in addr;
 
    if (sock < 0) sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
        return;
 
    addr.sin_family = AF_INET;
    addr.sin_port = htons(scl.serverport+2);
    addr.sin_addr.s_addr = INADDR_ANY;
 
    sendto(sock, buf, len, 0, (struct sockaddr*)&addr, sizeof(addr));
}

1. 299452 2540.827394285 127.0.0.1 127.0.0.1 GVSP 66 Unknown Format (0x0) [Block ID: 0 Packet ID: 0] Unknown Payload Type (0x0)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>
#include <ctype.h>
#include <winsock.h>
 
static int sock = -1;
 
void sendudptolocal(char *buf, int len)
{
    struct sockaddr_in addr;
    if (sock < 0) sock = socket(AF_INET, SOCK_DGRAM, 0);
    if (sock < 0)
        return;
 
    memset(&addr, 0, sizeof addr);
    addr.sin_family = AF_INET;
    addr.sin_port = htons(12345);
    addr.sin_addr.s_addr = inet_addr("127.0.0.1" );
 
    sendto(sock, buf, len, 0, (struct sockaddr*)&addr, sizeof(addr));
}
 
int main(void)
{
    WSADATA wsaData;
    WSAStartup(MAKEWORD(1,1), &wsaData);
 
    sendudptolocal("HELLO ", 6);
    sendudptolocal("WORLD!", 6);
    closesocket(sock);
    return 0;
}