网络编程：协议拆分练习（通过协议控制机械臂 TFTP传输文件）

一.使用代码控制机械臂

1.1协议要求以及操作

机械臂程序 使用 QT 写的一个windows下运行的 TCP 服务器

运行在哪个主机上 ip地址就是哪个主机的IP地址 端口号就是自己指定的 控制端口号

点击开启监听 就ok了 就开始等待客户端连接了

机械臂的协议：0xff 0x02 (1) (2) 0xff

(1) 要操作的摆臂 0x00 红色的摆臂 0x01 控制蓝色的摆臂

(2) 要偏移的角度

红 [-90, 90] char

蓝 [0, 180] unsigned char

1.2代码实现：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
#define ERRLOG(msg) do{\
        printf("%s %s(%d):", __FILE__, __func__, __LINE__);\
        perror(msg);\
        exit(-1);\
    }while(0)
 
int main(int argc, char const *argv[])
{
    if(3 != argc){
        printf("Usage: %s  \n", argv[0]);
        return -1;
    }
 
    int socketfd;
    if (-1 == (socketfd = socket(AF_INET, SOCK_STREAM, 0))){
        ERRLOG("socket error");
    }
 
    struct sockaddr_in clientaddr;
    clientaddr.sin_family = AF_INET;
    clientaddr.sin_port = htons(atoi(argv[2]));
    clientaddr.sin_addr.s_addr = inet_addr(argv[1]);
    socklen_t clientaddr_len = sizeof(clientaddr);
    
    if (-1 == connect(socketfd, (struct sockaddr*)&clientaddr, sizeof(clientaddr))){
        ERRLOG("connect error");
    }
 
    printf("连接成功\n");
 
    char red_buff[5] = {0xff, 0x02, 0x00, 0x00, 0xff};
    unsigned char blue_buff[5] = {0xff, 0x02, 0x01, 0x00, 0xff};
 
    if (-1 == send(socketfd, red_buff, 5, 0)){
        ERRLOG("send red_buf error");
    }
 
    sleep(1);
 
    if (-1 == send(socketfd, blue_buff, 5, 0)){
        ERRLOG("send blue_buff error");
    }
 
    char choose;
    while (1){
        printf("请输入您的选择(red+/- w/s blue+/- a/d)");
        scanf("%c", &choose);
        getchar();
 
        switch (choose){
            case 'w':
                if (red_buff[3] < 90){
                    red_buff[3] += 10;
                    if (-1 == send(socketfd, red_buff, 5, 0)){
                        ERRLOG("send red_buf error");
                    }
                }
                break;
            case 's':
                if (red_buff[3] > -90){
                    red_buff[3] -= 10;
                    if (-1 == send(socketfd, red_buff, 5, 0)){
                        ERRLOG("send red_buf error");
                    }
                }
                break;
            case 'a':
                if (blue_buff[3] < 180){
                    blue_buff[3] += 10;
                    if (-1 == send(socketfd, blue_buff, 5, 0)){
                        ERRLOG("send red_buf error");
                    }
                }
                break;
            case 'd':
                if (blue_buff[3] > 0){
                    blue_buff[3] -= 10;
                    if (-1 == send(socketfd, blue_buff, 5, 0)){
                        ERRLOG("send red_buf error");
                    }
                }
				break;
            case 'q':
                goto ret;
        }
    }
 
ret:
    return 0;
}

二TFTP协议练习

2.1 TFTP简介、通信过程

2.1.1 TFTP概述

TFTP：简单文件传送协议

最初用于引导无盘系统，被设计用来传输小文件

2.1.2 特点：

基于UDP协议实现

不进行用户有效性认证

2.1.3 数据传输模式：

octet：二进制模式

netascii：文本模式

mail：已经不再支持

2.2 TFTP通信过程

2.3 TFTP通信过程总结（无选项）

1、服务器在69号端口等待客户端的请求

2、服务器若批准此请求,则使用临时端口与客户端进行通信

3、每个数据包的编号都有变化（从1开始）

4、每个数据包都要得到ACK的确认如果出现超时,则需要重新发送最后的包（数据或ACK）

5、数据的长度以512Byte传输

6、小于512Byte的数据意味着传输结束

2.4 TFTP协议分析

错误码：

0 未定义,参见错误信息

1 File not found.

2 Access violation.

3 Disk full or allocation exceeded.

4 illegal TFTP operation.

5 Unknown transfer ID.

6 File already exists.

7 No such user.

8 Unsupported option(s) requested.

2.5代码实现：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
 
#define ERRLOG(msg) do{\
        printf("%s %s(%d):", __FILE__, __func__, __LINE__);\
        perror(msg);\
        exit(-1);\
    }while(0)
 
int main(int argc, char const *argv[])
{
    if (argc != 3){
        printf("输入的格式错误\n");
        exit(-1);
    }
 
    int socketfd;
    int nbytes;
    int fd;
    unsigned char buff[600] = {0};
    char filename[32] = {0};
    char text[512] = {0};
    unsigned short code;
    unsigned short number;
    unsigned short block_number = 0;
    
 
    if (-1 == (socketfd = socket(AF_INET, SOCK_DGRAM, 0))){
        ERRLOG("socket error");
    }
 
    struct sockaddr_in serveraddr;
    memset(&serveraddr, 0, sizeof(serveraddr));
    serveraddr.sin_family = AF_INET;
rename:
    serveraddr.sin_port = htons(atoi(argv[2]));
    serveraddr.sin_addr.s_addr = inet_addr(argv[1]);
    socklen_t serveraddr_len = sizeof(serveraddr);
 
    printf("请输入您要传输的文件");
    fgets(filename, sizeof(filename), stdin);
    filename[strlen(filename) - 1] = '\0';
 
    nbytes = sprintf(buff, "%c%c%s%c%s%c", 0, 1, filename, 0, "octet", 0);
    
    if (-1 == sendto(socketfd, buff, nbytes, 0, (struct sockaddr*)&serveraddr, serveraddr_len)){
        ERRLOG("sendto error");
    }
   
    while (1){
        if (-1 == (nbytes = recvfrom(socketfd, buff, sizeof(buff), 0, (struct sockaddr*)&serveraddr, &serveraddr_len))){
            ERRLOG("recvfrom error");
        }
 
        code = ntohs(*(unsigned short*)buff);
        number = ntohs(*(unsigned short*)(buff+2));
        strncpy(text, buff+4, nbytes-4);
 
        if (code == 3 && number == block_number+1){
            block_number++;
 
            if (number == 1){
                if (-1 == (fd = open(filename, O_RDWR | O_CREAT | O_TRUNC, 0666))){
                    ERRLOG("open error");
                }
            }
 
            write(fd, text, nbytes - 4);
 
            *(unsigned short*)buff = htons(4);
            *(unsigned short*)(buff+2) = htons(number);
 
            if (-1 == sendto(socketfd, buff, 4, 0, (struct sockaddr*)&serveraddr, serveraddr_len)){
                ERRLOG("sendto error");
            }
 
            if (nbytes - 4< 512){
                close(fd);
                break;
            }
        }else if(code == 5){
            printf("错误\n");
            goto rename;
        }
    }
 
    close(socketfd);
    return 0;
}