scoket编程（文件传输）

    写完了一个简单的聊天程序，我想如果我们要发送一个文件给对方的话，应该也可以用这个解决。其实我感觉TCP服务器端依次调用socket()、bind()、listen()之后，就会监听指定的socket地址了。TCP客户端依次调用socket()、connect()之后就向TCP服务器发送了一个连接请求。TCP服务器监听到这个请求之后，就会调用accept()函数去接收请求，这样连接就建立好了。之后就可以开始网络I/O操作了，即类同于普通文件的读写I/O操作。如果我们要实现文本信息传输的话只需要用send()和recv()函数就可以实现了。如果要实现文件传输的话只需从文件中读取出来在用send()发送，然后recv()接受的话再存到文件里就OK了。

  下面是实现的是客户端向服务端发送一个文件名，然后服务端接受到这个名字之后将该文件传送给客户端：

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

#define PORT    5552
#define LISTEN     20
#define BUFFER_SIZE    1024
#define MAX_SIZE         512

int main(int argc, char **argv)
{
    // 设置一个socket地址结构server_addr,代表服务器internet的地址和端口
    struct sockaddr_in   server_addr;
    bzero(&server_addr, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htons(INADDR_ANY);
    server_addr.sin_port = htons(PORT);

    // 创建用于internet的流协议(TCP)socket，用server_socket代表服务器向客户端提供服务的接口
    int server_socket = socket(PF_INET, SOCK_STREAM, 0);
    if (server_socket < 0)
    {
        printf("Create Socket Failed!\n");
        exit(1);
    }

    // 把socket和socket地址结构绑定
    if (bind(server_socket, (struct sockaddr*)&server_addr, sizeof(server_addr)))
    {
        printf("Server Bind Port: %d Failed!\n",PORT);
        exit(1);
    }

    // server_socket用于监听
    if (listen(server_socket,LISTEN))
    {
        printf("Server Listen Failed!\n");
        exit(1);
    }

    // 服务器端一直运行用以持续为客户端提供服务
    while(1)
    {
        struct sockaddr_in client_addr;
        socklen_t          length = sizeof(client_addr);

        // accpet返回一个新的socket,这个socket用来与此次连接到server的client进行通信
        int new_server_socket = accept(server_socket, (struct sockaddr*)&client_addr, &length);
        if (new_server_socket < 0)
        {
            printf("Server Accept Failed!\n");
            break;
        }

        char buffer[BUFFER_SIZE];
        memset(buffer,0,sizeof(buffer));
        length = recv(new_server_socket, buffer, BUFFER_SIZE, 0);
        if (length < 0)
        {
            printf("Server Recieve Data Failed!\n");
            break;
        }

        char file_name[MAX_SIZE + 1];
        memset(file_name,0,sizeof(file_name));
        strncpy(file_name, buffer,
                strlen(buffer) > MAX_SIZE ? MAX_SIZE : strlen(buffer));

        FILE *fp = fopen(file_name, "r");
        if (fp == NULL)
        {
            printf("File:\t%s Not Found!\n", file_name);
        }
        else
        {
            memset(buffer,0, BUFFER_SIZE);
            int file_block_length = 0;
            while( (file_block_length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
            {
                printf("file_block_length = %d\n", file_block_length);

                // 发送buffer中的字符串到new_server_socket,实际上就是发送给客户端
                if (send(new_server_socket, buffer, file_block_length, 0) < 0)
                {
                    printf("Send File:\t%s Failed!\n", file_name);
                    break;
                }

                memset(buffer,0,sizeof(buffer));
            }
            fclose(fp);
            printf("File:\t%s Transfer Finished!\n", file_name);
        }

        close(new_server_socket);
    }

    close(server_socket);

    return 0;
}

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

#define PORT       5552
#define BUFFER_SIZE     1024
#define MAX_SIZE       512

int main(int argc, char **argv)
{
    if (argc != 2)
    {
        printf("IP error\n");
        exit(1);
    }
    // 创建用于internet的流协议(TCP)类型socket，用client_socket代表客户端socket
    int client_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (client_socket < 0)
    {
        printf("Create Socket Failed!\n");
        exit(1);
    }
    // 设置一个socket地址结构server_addr,代表服务器的internet地址和端口
    struct sockaddr_in  server_addr;
    memset(&server_addr,0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;

    // 服务器的IP地址来自程序的参数
    if (inet_aton(argv[1], &server_addr.sin_addr) == 0)
    {
        printf("Server IP Address Error!\n");
        exit(1);
    }

    server_addr.sin_port = htons(PORT);
    socklen_t server_addr_length = sizeof(server_addr);

    // 向服务器发起连接请求，连接成功后client_socket代表客户端和服务器端的一个socket连接
    if (connect(client_socket, (struct sockaddr*)&server_addr, server_addr_length) < 0)
    {
        printf("Can Not Connect To %s!\n", argv[1]);
        exit(1);
    }

    char file_name[MAX_SIZE + 1];
    memset(file_name,0, sizeof(file_name));
    printf("Please Input T he File Name On Server.\t");
    scanf("%s", file_name);

    char buffer[BUFFER_SIZE];
    memset(buffer,0, sizeof(buffer));
    strncpy(buffer, file_name, strlen(file_name) > BUFFER_SIZE ? BUFFER_SIZE : strlen(file_name));
    // 向服务器发送buffer中的数据，此时buffer中存放的是客户端需要接收的文件的名字
    send(client_socket, buffer, BUFFER_SIZE, 0);

    FILE *fp = fopen(file_name, "w");
    if (fp == NULL)
    {
        printf("File:\t%s Can Not Open To Write!\n", file_name);
        exit(1);
    }

    // 从服务器端接收数据到buffer中
    memset(buffer,0, sizeof(buffer));
    int length = 0;
    while(length = recv(client_socket, buffer, BUFFER_SIZE, 0))
    {
        if (length < 0)
        {
            printf("Recieve Data From Server %s Failed!\n", argv[1]);
            break;
        }

        int write_length = fwrite(buffer, sizeof(char), length, fp);
        if (write_length < length)
        {
            printf("File:\t%s Write Failed!\n", file_name);
            break;
        }
        memset(buffer,0, BUFFER_SIZE);
    }

    printf("Recieve File:\t %s From Server[%s] Finished!\n", file_name, argv[1]);

    // 传输完毕，关闭socket
    fclose(fp);
    close(client_socket);
    return 0;

}

  运行之后的截图:

lwp@lwp-linux:~/Desktop$ ./cli 192.168.200.180
Please Input T he File Name On Server. data
Recieve File:	 liwenping From Server[192.168.200.180] Finished!

lwp@lwp-linux:~/Desktop$ ./ser
File:    data Transfer

这样我们就将服务端的data文件传输到了客户端。