Example C program for curl issue #5717

main.c

#include <curl/curl.h>
#include <errno.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>

#define EXPECT(expr)                                  \
    {                                                 \
        if (expr != 0)                                \
        {                                             \
            fprintf(stderr, "%s\n", strerror(errno)); \
            exit(1);                                  \
        }                                             \
    }

#define CURL_EXPECT(expr)                                        \
    {                                                            \
        CURLcode result;                                         \
        if ((result = expr) != CURLE_OK)                         \
        {                                                        \
            fprintf(stderr, "%s\n", curl_easy_strerror(result)); \
            exit(1);                                             \
        }                                                        \
    }

static void *server_main(void *arg)
{
    int server_socket = (int)arg;
    int client_socket, len;
    struct sockaddr_in client_addr;
    socklen_t addr_len = sizeof(client_addr);

    if ((client_socket = accept(server_socket, &client_addr, &addr_len)) < 0)
    {
        fprintf(stderr, "Accept failed\n");
        exit(1);
    }

    char buf[8192];
    recv(client_socket, buf, 65535, 0);

    FILE *fd = fdopen(client_socket, "w");
    fprintf(fd, "HTTP/1.1 200 OK\r\n");
    fprintf(fd, "Content-Length: 0\r\n\r\n");
    fflush(fd);

    EXPECT(close(client_socket));
    EXPECT(close(server_socket));

    return NULL;
}

int main(int argc, char **argv)
{
    CURLcode result;
    int server_socket, len;
    pthread_t server_thread;

    CURL_EXPECT(curl_global_init(CURL_GLOBAL_ALL));

    // Create a server socket.
    if ((server_socket = socket(AF_INET, SOCK_STREAM, 0)) < 0)
    {
        fprintf(stderr, "Socket creation failed\n");
        exit(1);
    }

    struct sockaddr_in server_addr;
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(0);
    server_addr.sin_addr.s_addr = INADDR_ANY;

    len = sizeof(server_addr);
    EXPECT(bind(server_socket, &server_addr, len));
    EXPECT(listen(server_socket, 10000));
    getsockname(server_socket, &server_addr, &len);

    char url[64];
    sprintf(url, "http://127.0.0.1:%d", ntohs(server_addr.sin_port));

    // Spawn TCP server thread.
    pthread_create(&server_thread, NULL, server_main, (void *)server_socket);

    CURL *curl = curl_easy_init();

    FILE *infile = fopen("main.c", "rb");
    fseek(infile, 0L, SEEK_END);
    long infile_size = ftell(infile);
    fseek(infile, 0L, SEEK_SET);

    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1);
    curl_easy_setopt(curl, CURLOPT_URL, &url);
    curl_easy_setopt(curl, CURLOPT_READDATA, infile);
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, fread);
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1);
    curl_easy_setopt(curl, CURLOPT_NOBODY, 1);
    curl_easy_setopt(curl, CURLOPT_CUSTOMREQUEST, "HEAD");
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, infile_size);

    CURL_EXPECT(curl_easy_perform(curl));

    curl_easy_cleanup(curl);
    fclose(infile);

    return 0;
}

Makefile

.PHONY: run-old
run-old: out/old
	$<

.PHONY: run-new
run-new: out/new
	$<

.PHONY: clean
clean:
	rm -r out

out/old: main.c
	mkdir -p $(@D)
	gcc -o $@ $< -lcurl -lpthread

out/new: main.c
	mkdir -p $(@D)
	gcc -o $@ $< /usr/local/lib/libcurl.a -lpthread -lssl -lcrypto

My C is a little rusty so this is probably not the most well-written program, but it gets the job done.