Stupid UDP sender

udpsend.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <assert.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>

#define MAX_PACKET 20000U

void usage(void) {
    puts("\nUsage: udpsend <host> <port>\n");
    exit(EXIT_SUCCESS);
}

struct addrinfo *resolve(const char * const host, const char * const port)
{
    struct addrinfo *ai, hints;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_flags = 0;
    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_protocol = IPPROTO_UDP;
    const int gai_err = getaddrinfo(host, port, &hints, &ai);
    assert(gai_err == 0);

    return ai;
}

int main(int argc, char *argv[])
{
    if (argc != 3) {
        usage();
    }
    const char * const host = argv[1];
    const char * const port = argv[2];
    struct addrinfo *ai = resolve(host, port);
    int kindy = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    char buf[MAX_PACKET];
    const ssize_t nbread = read(0, buf, sizeof buf);
    assert(nbread > (ssize_t) 0);
    assert(sendto(kindy, buf, nbread, 0, ai->ai_addr, ai->ai_addrlen)
           == nbread);
    assert(kindy != -1);
    freeaddrinfo(ai);
    close(kindy);
    
    return 0;
}