6-3-sendfile.c

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

int main(int argc, const char *argv[])
{
    if (argc <= 3) 
    {
        fprintf(stderr, "usage: %s ip_address port_number filename\n", basename(argv[0]));
        return 1;
    }
    const char *ip = argv[1];
    int port       = atoi(argv[2]);
    const char *file_name = argv[3];
    
    int filefd = open(file_name, O_RDONLY);
    assert( filefd > 0);
    struct stat stat_buf;
    fstat(filefd, &stat_buf);

    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port   = htons(port);

    int sock = socket(AF_INET, SOCK_STREAM, 0);
    assert(sock > 0);

    int ret = bind(sock, (struct sockaddr *)&address, sizeof(address));
    assert(ret != -1);

    ret = listen(sock, 5);
    assert(ret != -1);

    struct sockaddr_in client;
    socklen_t client_addrlength = sizeof(client);
    int connfd = accept(sock, (struct sockaddr *)&client, &client_addrlength);
    if(connfd < 0)
    {
        fprintf(stderr, "accept error! errno:%d, errstr:%s\n", errno, strerror(errno));
    }
    else
    {
        sendfile(connfd, filefd, NULL, stat_buf.st_size);
        close(connfd);
    }

    close(filefd);
    close(sock);
    return 0;
}