#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/stat.h>
#include <sys/sendfile.h>

int main(int argc, char **argv)
{
	int sock;
	int ret;
	int desc;
	int fd;
	int len;
	unsigned short port = 5000;
	char fname[128];
	char fsize[12];
	off_t offset = 0;
	struct sockaddr_in addr;
	struct sockaddr_in addr2;
	struct stat stat_buf;

	sock = socket(AF_INET, SOCK_STREAM, 0);
	if (sock == -1) {
		perror("socket()");
		fprintf(stderr, "socket failed\n");
		exit(1);
	}

	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = INADDR_ANY;
	addr.sin_port = htons(port);

	ret =  bind(sock, (struct sockaddr *) &addr, sizeof(addr));
	if (ret) {
		perror("bind()");
		fprintf(stderr, "bind socket failed\n");
		exit(1);
	}

	/* listen for client */
	ret = listen(sock, 1);
	if (ret) {
		perror("listen()");
		fprintf(stderr, "listen failed\n");
		exit(1);
	}

	while (1) {
		len = sizeof(struct sockaddr);
		desc = accept(sock, (struct sockaddr *) &addr2, &len);
		if (desc == -1) {
			perror("accept()");
			fprintf(stderr, "accept failed\n");
			exit(1);
		}

		/* get the file name from the client and open it */
		ret = recv(desc, fname, sizeof(fname), 0);
		if (ret == -1) {
			perror("recv()");
			fprintf(stderr, "recv failed\n");
			exit(1);
		}
		fname[ret] = '\0';
		fd = open(fname, O_RDONLY);
		if (fd == -1) {
			perror("open()");
			fprintf(stderr, "unable to open '%s'\n", fname);
			exit(1);
		}

		/* get the size of the file and tell the client */
		fstat(fd, &stat_buf);
		sprintf(fsize, "%d", stat_buf.st_size);
		ret = send(desc, fsize, strlen(fsize), 0);
		if (ret == -1) {
			perror("send()");
			fprintf(stderr, "send failed\n");
			exit(1);
		}

		fprintf(stderr, "sending file '%s' size %d bytes\n",
			fname, stat_buf.st_size);

		/* send the file */
		offset = 0;
		ret = sendfile(desc, fd, &offset, stat_buf.st_size);
		if (ret == -1) {
			perror("sendfile()");
			fprintf(stderr, "sendfile failed\n");
			exit(1);
		}
		fprintf(stderr, "%d bytes sent\n", ret);

		/* did the whole file get sent? */
		if (ret != stat_buf.st_size) {
			fprintf(stderr, "error: %d of %d bytes transferred\n",
				ret, (int) stat_buf.st_size);
			exit(1);
		}
		close(fd);
		close(desc);
	}
	close(sock);
	exit(0);
}