通过Socket通过Client向Server使用sendfile传文件

本文链接：https://blog.youkuaiyun.com/amaowolf/article/details/7420234

本文介绍了一个使用Linux Socket的sendfile系统调用实现客户端到服务器的文件传输，利用zero copy技术提高效率。服务器端根据当前时间生成唯一文件名保存接收到的文件。

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1. server.c

(a)为了将传过来的文件保存为不同的文件内容，故用本机时间的十六进制作为文件名

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#include<sys/stat.h>
#include<fcntl.h>
#include<time.h>

#include<errno.h>
#define oops(msg) { perror(msg); exit(errno); }

int main(){
        int sd = socket(PF_INET, SOCK_STREAM, 0);
        if(sd == -1) oops("socket");

        struct sockaddr_in address;
        bzero((void *)&address, sizeof(address));
        address.sin_family = AF_INET;
        address.sin_addr.s_addr = inet_addr("192.168.227.128");
        address.sin_port =  8888;

        int bind_return =  bind(sd, (struct sockaddr *)&address, sizeof(address));
        if(bind_return == -1) oops("bind");

        int listen_return = listen(sd, 1);
        if(listen_return == -1) oops("listen");

        while(1){
                int client_fd = accept(sd, NULL, NULL);
                if(client_fd == -1) oops("accept");

                time_t current_time = time(NULL);
                char fileName[50];
                sprintf(fileName, "/root/study/socket/%x", current_time);
                int fd = open(fileName, O_WRONLY|O_CREAT, S_IRUSR|S_IWUSR);
                if(fd == -1) oops("open");

                char buff[1024];
                ssize_t length;
                while((length = recv(client_fd, buff, sizeof(buff), 0)) > 0){
                        write(fd, buff, length);
                }

                close(fd);
        }
        return EXIT_SUCCESS;
}

2. client.c

(1) 通过sendfile进行内核空间向socket传文件，也就是所为的zero copy。

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>

#include<sys/types.h>
#include<sys/socket.h>
#include<sys/sendfile.h>
#include<netinet/in.h>
#include<arpa/inet.h>

#include<sys/stat.h>
#include<fcntl.h>

#include<errno.h>

#define oops(msg) { perror(msg); exit(errno); }

int main(int argc, char *argv[]){
        if(argc != 2)oops("which file not specified?");

        int sd = socket(PF_INET, SOCK_STREAM, 0);
        if(sd == -1) oops("socket");

        struct sockaddr_in address;
        bzero(&address, sizeof(address));
        address.sin_family = AF_INET;
        address.sin_addr.s_addr = inet_addr("192.168.227.128");
        address.sin_port =  8888;

        int connect_ret = connect(sd, (struct sockaddr*)&address, sizeof(address));
        if(connect_ret == -1) oops("connect");

        int fd = open(argv[1], O_RDONLY);
        off_t offset = 0;
        struct stat fileStatus;
        int fstat_ret = fstat(fd, &fileStatus);
        if(fstat_ret == -1)oops("fstat");

        ssize_t length = sendfile(sd, fd, &offset, fileStatus.st_size);
        if(length == -1)
                {oops("sendfile");}
        else
                fprintf(stdout, "%ld characters have been send to server.\n", length);

        close(fd);

        close(sd);
        return EXIT_SUCCESS;
}