嵌入式学习——Linux高级编程复习（UDP编程）——day43

Spcarrydoinb2024-06-19 21:11
  1. UDP编程------函数接口

1.1 socket

  1. 定义

int socket(int domain, int type, int protocol);

  1. 功能

创建一个用来进程通信的套接字,返回文件描述符

  1. 参数

domain:AF_INET IPv4协议族

type:SOCK_STREAM 流式套接字 tcp传输协议

SOCK_DGRAM 数据报套接字 udp传输协议

SOCK_RAW 原始套接字

protocol:

默认为0

  1. 返回值

成功返回套接字新文件描述符

失败返回-1

  1. 注意

1.2 inet_addr

  1. 定义

in_addr_t inet_addr(const char *cp);

  1. 功能

将字符串IP地址转换为二进制IP地址

  1. 参数

cp:字符串IP地址空间首地址

  1. 返回值

成功返回二进制IP地址

  1. 注意

1.3 htons

  1. 定义

uint16_t htons(uint16_t hostshort);

  1. 功能

将本地字节序（小端）转换为网络字节序（大端）

  1. 参数

hostshort:本地端口号

  1. 返回值

返回网络字节序端口号

uint16_t ntohs(uint16_t netshort);

功能:

将网络字节序（大端）转换为本地字节序（小端）

1.4 bind

  1. 定义

int bind(int sockfd, const struct sockaddr *addr,

socklen_t addrlen);

  1. 功能

将套接字与IP地址端口绑定在一起

  1. 参数

sockfd:文件描述符

addr:结构体空间首地址

addrlen:信息的长度

  1. 返回值

成功返回0

失败返回-1

  1. 注意

1.5 sendto

  1. 定义

ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,

const struct sockaddr *dest_addr, socklen_t addrlen);

  1. 功能

给另一个套接字发送消息

  1. 参数

sockfd:套接字文件描述符

buf:要发送数据存放空间的首地址

len:要发送数据的长度

flags:发送属性 默认为0

dest_addr:目的地址

addrlen:目的地址信息长度

struct sockaddr_in {

sa_family_t sin_family; /* address family: AF_INET */（协议族）

in_port_t sin_port; /* port in network byte order */（端口号、小端存储要改成大端存储）

struct in_addr sin_addr; /* internet address */（IP地址）

};

/* Internet address. */

struct in_addr {

uint32_t s_addr; /* address in network byte order */

};

  1. 返回值

成功返回发送字节个数

失败返回-1

1.6 recvfrom

  1. 定义

ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,

struct sockaddr *src_addr, socklen_t *addrlen);

  1. 功能

接收数据

  1. 参数

sockfd:套接字文件描述符

buf:存放接收到数据空间的首地址

len:最多允许接收的字节数

flags:属性 默认为0

src_addr:存放发送端地址信息空间首地址

addrlen:想要接收发送端地址大小的变量空间首地址

  1. 返回值

成功返回实际接收字节数

失败返回-1

  1. 注意

该函数具有阻塞功能

  1. UDP编程示例程序

2.1 单方向收发

  1. 头文件
cpp 复制代码 
#ifndef __HEAD_H__
#define __HEAD_H__

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

#endif

2.发送端代码（send.c）

cpp 复制代码 
#include "head.h"

int main(int argc, char const *argv[])
{
	int sockfd = 0;
	char tmpbuff[1024] = {"hello world"};
	struct sockaddr_in recvaddr;
	ssize_t nsize = 0;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	if (-1 == sockfd)
	{
		perror("fail to socket");
		return -1;
	}

	recvaddr.sin_family = AF_INET;
	recvaddr.sin_port = htons(50000);
	recvaddr.sin_addr.s_addr = INADDR_ANY；
	nsize = sendto(sockfd, tmpbuff, strlen(tmpbuff)+1, 0, (struct sockaddr *)&recvaddr, sizeof(recvaddr));
	if (-1 == nsize)
	{
		perror("fail to sendto");
		return -1;
	}

	printf("send %ld bytes success\n", nsize);

	close(sockfd);

	return 0;
}
  1. 接收端代码（recv.c）
cpp 复制代码 
#include "head.h"

int main(int argc, char const *argv[])
{
	int sockfd = 0;
	int ret = 0;
	ssize_t nsize = 0;
	char tmpbuff[4096] = {0};
	struct sockaddr_in recvaddr;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	if (-1 == sockfd)
	{
		perror("fail to socket");
		return -1;
	}

	recvaddr.sin_family = AF_INET;
	recvaddr.sin_port = htons(50000);
	recvaddr.sin_addr.s_addr = INADDR_ANY;
	ret = bind(sockfd, (struct sockaddr *)&recvaddr, sizeof(recvaddr));
	if (-1 == ret)
	{
		perror("fail to bind");
		return -1;
	}

	nsize = recvfrom(sockfd, tmpbuff, sizeof(tmpbuff), 0, NULL, NULL);
	if (-1 == nsize)
	{
		perror("fail to recvfrom");
		return -1;
	}

	printf("recv %ld bytes success\n", nsize);
	printf("RECV:%s\n", tmpbuff);

	close(sockfd);

	return 0;
}

2.2 双向通信

  1. 头文件
cpp 复制代码 
#ifndef __HEAD_H__
#define __HEAD_H__

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

#endif

2.发送端代码（send.c）

cpp 复制代码 
#include "head.h"

int main(int argc, char const *argv[])
{
	int sockfd = 0;
	char tmpbuff[4096] = {"你在吗?"};
	struct sockaddr_in recvaddr;
	ssize_t nsize = 0;

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	if (-1 == sockfd)
	{
		perror("fail to socket");
		return -1;
	}	

	recvaddr.sin_family = AF_INET;
	recvaddr.sin_port = htons(50000);
	recvaddr.sin_addr.s_addr = INADDR_ANY;
	nsize = sendto(sockfd, tmpbuff, strlen(tmpbuff)+1, 0, (struct sockaddr *)&recvaddr, sizeof(recvaddr));
	if (-1 == nsize)
	{
		perror("fail to sendto");
		return -1;
	}

	memset(tmpbuff, 0, sizeof(tmpbuff));
	nsize = recvfrom(sockfd, tmpbuff, sizeof(tmpbuff), 0, NULL, NULL);
	if (-1 == nsize)
	{
		perror("fail to recvfrom");
		return -1;
	}

	printf("RECV:%s\n", tmpbuff);

	close(sockfd);

	return 0;
}
  1. 接收端代码（recv.c）
cpp 复制代码 
#include "head.h"

int main(int argc, char const *argv[])
{
	int sockfd = 0;
	int ret = 0;
	struct sockaddr_in recvaddr;
	struct sockaddr_in sendaddr;
	char tmpbuff[4096] = {0};
	ssize_t nsize = 0;
	socklen_t addrlen = sizeof(sendaddr);

	sockfd = socket(AF_INET, SOCK_DGRAM, 0);
	if (-1 == sockfd)
	{
		perror("fail to socket");
		return -1;
	}	

	recvaddr.sin_family = AF_INET;
	recvaddr.sin_port = htons(50000);
	recvaddr.sin_addr.s_addr = INADDR_ANY;
	ret = bind(sockfd, (struct sockaddr *)&recvaddr, sizeof(recvaddr));
	if (-1 == ret)
	{
		perror("fail to bind");
		return -1;
	}

	nsize = recvfrom(sockfd, tmpbuff, sizeof(tmpbuff), 0, (struct sockaddr *)&sendaddr, &addrlen);
	if (-1 == nsize)
	{
		perror("fail to recvfrom");
		return -1;
	}

	printf("[%s:%d]%s\n", inet_ntoa(sendaddr.sin_addr), ntohs(sendaddr.sin_port), tmpbuff);

	sprintf(tmpbuff, "%s --------echo", tmpbuff);
	nsize = sendto(sockfd, tmpbuff, strlen(tmpbuff), 0, (struct sockaddr *)&sendaddr, sizeof(sendaddr));
	if (-1 == nsize)
	{
		perror("fail to sendto");
		return -1;
	}

	close(sockfd);

	return 0;
}

2.3 使用UDP进行文件复制（CP）

1.服务端

cpp 复制代码 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>
#include <fcntl.h>

typedef struct sockaddr * (SA);

int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(-1 == sockfd)
    {
        perror("socket");
        exit(1);
    }
    struct sockaddr_in ser,cli;
    //man 7 ip 
   bzero(&ser,sizeof(ser)); 
   bzero(&cli,sizeof(ser));
   ser.sin_family = AF_INET;
   ser.sin_port  = htons(50000);//host to net  short 
   ser.sin_addr.s_addr = INADDR_ANY ;//inet_addr("127.0.0.1")
    int ret = bind(sockfd,(SA)&ser,sizeof(ser));
    if(-1 == ret)
    {
        perror("bind");
        exit(1);
    }
    int fd = open("2.png",O_CREAT|O_WRONLY|O_TRUNC,0666);
    if(-1 == fd)
    {
        perror("open");
        exit(1);
    }
    while(1)
    {
        char buf[1024]={0};
        socklen_t len = sizeof(cli);
        int rd_ret = recvfrom(sockfd,buf,sizeof(buf),0,(SA)&cli,&len);
        if(0 == strcmp(buf,"^_^"))
        {
            break;
        }
        write(fd,buf,rd_ret);
        bzero(buf,sizeof(buf));
        strcpy(buf,"go on");
        sendto(sockfd,buf,strlen(buf),0,(SA)&cli,sizeof(cli));
    }
    close(fd);
    close(sockfd);
    return 0;
}
  1. 客户端
cpp 复制代码 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <fcntl.h>

typedef struct sockaddr * (SA);
int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(-1 == sockfd)
    {
        perror("socket");
        exit(1);
    }
    struct sockaddr_in ser,cli;
    //man 7 ip 
    bzero(&ser,sizeof(ser)); 
    bzero(&cli,sizeof(ser));
    ser.sin_family = AF_INET;
    ser.sin_port = htons(50000);//host to net  short 
    ser.sin_addr.s_addr = INADDR_ANY;
    int fd = open("/home/linux/1.png",O_RDONLY);
    if(-1 == fd)
    {
        perror("open");
        exit(1);
    }
    char buf[1024]={0};
        socklen_t len = sizeof(ser);
    while(1)
    {
        bzero(buf,sizeof(buf));
        int rd_ret = read(fd,buf,sizeof(buf));
        if(rd_ret<=0)
        {
            break;
        }
        sendto(sockfd,buf,rd_ret,0,(SA)&ser,len);
        bzero(buf,sizeof(buf));
        recvfrom(sockfd,buf,sizeof(buf),0,NULL,NULL);
    }

    strcpy(buf,"^_^");
    sendto(sockfd,buf,strlen(buf),0,(SA)&ser,len);
    close(fd);
    close(sockfd);
    return 0;
}

2.4 使用UDP进行两端聊天（chat）

  1. 服务端
cpp 复制代码 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>
#include <pthread.h>

typedef struct sockaddr * (SA);

struct sockaddr_in ser,cli;

void* th1(void* arg)
{
    int sockfd =* (int*)arg;
    while(1)
    {
        char buf[256]={0};
        socklen_t len = sizeof(cli);
        recvfrom(sockfd,buf,sizeof(buf),0,NULL,NULL);
        printf("from c:%s\n",buf);

    }

}

void* th2(void* arg)
{
    int sockfd =* (int*)arg;
    while(1)
    {
    
        printf("to c:");
        char buf[256]={0};
        fgets(buf,sizeof(buf),stdin);
        buf[strlen(buf)-1]='\0';
        sendto(sockfd,buf,strlen(buf),0,(SA)&cli,sizeof(cli));
    
    }

}

int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(-1 == sockfd)
    {
        perror("socket");
        exit(1);
    }
    //man 7 ip 
   bzero(&ser,sizeof(ser)); 
   bzero(&cli,sizeof(ser));
   ser.sin_family = AF_INET;
   ser.sin_port  = htons(50000);//host to net  short 
   ser.sin_addr.s_addr = INADDR_ANY;
    int ret = bind(sockfd,(SA)&ser,sizeof(ser));
    if(-1 == ret)
    {
        perror("bind");
        exit(1);
    }
    pthread_t tid1,tid2;
    socklen_t len = sizeof(cli);
    char buf[256]={0};
    recvfrom(sockfd,buf,sizeof(buf),0,(SA)&cli,&len);
    pthread_create(&tid1,NULL,th1,&sockfd);
    pthread_create(&tid2,NULL,th2,&sockfd);

    pthread_join(tid1,NULL);
    pthread_join(tid2,NULL);
    return 0;
}
  1. 客户端
cpp 复制代码 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>          /* See NOTES */
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <pthread.h>


typedef struct sockaddr * (SA);


struct sockaddr_in ser,cli;
void* th1(void* arg)
{
    int sockfd =* (int*)arg;
    while(1)
    {
        char buf[256]={0};
        socklen_t len = sizeof(cli);
        recvfrom(sockfd,buf,sizeof(buf),0,NULL,NULL);
        printf("from s:%s\n",buf);

    }

}
void* th2(void* arg)
{
    int sockfd =* (int*)arg;
    while(1)
    {
    
        printf("to s");
        char buf[256]={0};
        fgets(buf,sizeof(buf),stdin);
        buf[strlen(buf)-1]='\0';
        sendto(sockfd,buf,strlen(buf),0,(SA)&ser,sizeof(ser));
    
    }

}
int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET,SOCK_DGRAM,0);
    if(-1 == sockfd)
    {
        perror("socket");
        exit(1);
    }
    //man 7 ip 
    bzero(&ser,sizeof(ser)); 
    bzero(&cli,sizeof(ser));
    ser.sin_family = AF_INET;
    ser.sin_port  = htons(50000);//host to net  short 
    ser.sin_addr.s_addr = INADDR_ANY; 
    pthread_t tid1,tid2;
    char buf[256]="start";
    sendto(sockfd,buf,strlen(buf),0,(SA)&ser,sizeof(ser));
    pthread_create(&tid1,NULL,th1,&sockfd);
    pthread_create(&tid2,NULL,th2,&sockfd);

    pthread_join(tid1,NULL);
    pthread_join(tid2,NULL);

    return 0;
}
  1. UDP特性

1.实现简单

2.占用资源较小

3.不安全、不可靠

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