recvfrom
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,
struct sockaddr *src_addr, socklen_t *addrlen);
功能:
从套接字中接收数据
参数:
sockfd:套接字文件描述符
buf:存放数据空间首地址
flags:属性 默认为0
src_addr:存放IP地址信息的空间首地址
addrlen:存放接收到IP地址大小空间的首地址
返回值:
成功返回实际接收字节数
失败返回-1
修改虚拟机到桥接模式
点击"虚拟机"
点击"设置"
点击"网络适配器"
选择"桥接模式"
点击"确定"3.将网卡桥接到无线网卡
点击"编辑"
点击"虚拟网络编辑器"
点击"更改设置"4.在Ubuntu中重启网络服务
sudo /etc/init.d/networking restartifconfig
bind
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);
功能:
在套接字上绑定一个IP地址和端口号
参数:
sockfd:套接字文件描述符
addr:绑定IP地址空间首地址
addrlen:绑定IP地址的长度
返回值:
成功返回0
失败返回-1
UDP需要注意的细节点:
1.UDP是无连接,发端退出,收端没有任何影响
2.UDP发送数据上限,最好不要超过1500个字节
3.UDP是不安全不可靠的,连续且快速的传输数据容易产生数据丢失
UDP包头长度:8个字节
源端口号（2个字节）
目的端口号（2个字节）
长度（2个字节）
校验和（2个字节）
wireshark
抓包工具
操作流程:
1.sudo wireshark
打开wireshark抓包工具
2.选择抓取数据包的网卡
any
3.执行通信的代码
4.停止通信
5.设定过滤条件
ip.addr == IP地址
udp
tcp
udp.port == 端口
使用UDP实现文件的发送
发送端代码：
/*************************************************************************
> File Name: recv_file.c
> Author: yas
> Mail: rage_yas@hotmail.com
> Created Time: Wed 06 Mar 2024 02:11:43 PM CST
************************************************************************/
#include<stdio.h>
#include "head.h"
int main(void)
{
int sockfd = 0;
struct sockaddr_in sendaddr;
ssize_t nret = 0;
char filename[1024] = {0};
int pf = 0;
char tmpbuff[1024] = {0};
int nbyte = 0;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1)
{
perror("fail to socket");
return -1;
}
fgets(filename, sizeof(filename), stdin);
sendaddr.sin_family = AF_INET;
sendaddr.sin_port = htons(50000);
sendaddr.sin_addr.s_addr = inet_addr("192.168.1.174");
nbyte = sendto(sockfd, filename, strlen(filename), 0, (struct sockaddr *)&sendaddr, sizeof(sendaddr));
if (nbyte == -1)
{
perror("fail to sendto");
return -1;
}
pf = open(filename, O_RDONLY);
if (pf == -1)
{
perror("fail to open");
return -1;
}
while(1)
{
memset (tmpbuff, 0, sizeof(tmpbuff));
nret = read(pf, tmpbuff, sizeof(tmpbuff));
if(nret <= 0)
{
break;
}
nret = sendto(sockfd, tmpbuff, nret, 0, (struct sockaddr *)&sendaddr, sizeof(sendaddr));
}
close(pf);
close(sockfd);
return 0;
}接收端代码：
#include<stdio.h>
#include "head.h"
int main(void)
{
int sockfd = 0;
ssize_t nsize = 0;
struct sockaddr_in recvaddr;
struct sockaddr_in sendaddr;
ssize_t nret = 0;
char filename[1024] = {0};
socklen_t addlen = sizeof(recvaddr);
int pf = 0;
char tmpbuff[1024] = {0};
int retbind = 0;
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1)
{
perror("fail to socket");
return -1;
}
recvaddr.sin_family = AF_INET;
recvaddr.sin_port = htons(50000);
recvaddr.sin_addr.s_addr = inet_addr("192.168.1.174");
retbind = bind(sockfd, (struct sockaddr *)&recvaddr, sizeof(recvaddr));
if (retbind == -1)
{
perror("fail to bind");
return -1;
}
//printf("!!!!!!!!!!!\n");
nsize = recvfrom(sockfd, filename, sizeof(filename), 0,(struct sockaddr *)&sendaddr, &addlen);
if (-1 == nsize)
{
perror("fail to recvfrom");
return -1;
}
//printf("!!!!!!!!!!!\n");
//printf("filename = %s\n", filename);
pf = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0664);
if (pf == -1)
{
perror("fail to open");
return -1;
}
while(1)
{
memset (tmpbuff, 0, sizeof(tmpbuff));
nret = recvfrom(sockfd, tmpbuff, sizeof(tmpbuff), 0,(struct sockaddr *)&recvaddr, &addlen);
if (nret <= 0)
{
break;
}
write(pf, tmpbuff, nret);
}
close(pf);
close(sockfd);
return 0;
}使用UDP实现两个主机间的全双工通信
/************************************************************************* > File Name: homework.c > Author: yas > Mail: rage_yas@hotmail.com > Created Time: Wed 06 Mar 2024 06:09:58 PM CST ************************************************************************/ #include<stdio.h> #include "head.h" struct cilent { char name[32]; char text[1024]; }; struct cilent mycilent; struct cilent youcilent; void *pthreadSend(void *arg) { int sockid = 0; struct sockaddr_in recvaddr; int nret = 0; sockid = socket(AF_INET, SOCK_DGRAM, 0); if (sockid == -1) { perror("fail to socket"); return NULL; } recvaddr.sin_family = AF_INET; recvaddr.sin_port = htons(50000); recvaddr.sin_addr.s_addr = inet_addr("192.168.1.152"); scanf("%s", mycilent.name); nret = sendto(sockid, mycilent.name, sizeof(mycilent.name), 0, (struct sockaddr *)&recvaddr, sizeof(recvaddr)); if (nret == -1) { perror("fail to sendto"); return NULL; } while(1) { memset(mycilent.text, 0, sizeof(mycilent.text)); scanf("%s", mycilent.text); nret = sendto(sockid, mycilent.text, sizeof(mycilent.text), 0, (struct sockaddr *)&recvaddr, sizeof(recvaddr)); if (nret == -1) { perror("fail to sendto"); return NULL; } if(strcmp(mycilent.text, ".quit") == 0) { break; } } close(sockid); } void *pthreadRecv(void *argv) { int sockid = 0; struct sockaddr_in recvaddr; struct sockaddr_in getaddr; socklen_t addlen = sizeof(getaddr); int nret = 0; sockid = socket(AF_INET, SOCK_DGRAM, 0); if (sockid == -1) { perror("fail to socket"); return NULL; } recvaddr.sin_family = AF_INET; recvaddr.sin_port = htons(50000); recvaddr.sin_addr.s_addr = inet_addr("192.168.1.174"); bind(sockid, (struct sockaddr *)&recvaddr, sizeof(recvaddr)); nret = recvfrom(sockid, youcilent.name, sizeof(youcilent.name), 0, (struct sockaddr *)&getaddr, &addlen); if (nret == -1) { perror("fail to sendto"); return NULL; } while(1) { memset(youcilent.text, 0, sizeof(youcilent.text)); nret = recvfrom(sockid, youcilent.text, sizeof(youcilent.text), 0, (struct sockaddr *)&getaddr, &addlen); if (nret == -1) { perror("fail to sendto"); return NULL; } printf("%s(%s:%d)>%s\n", youcilent.name, inet_ntoa(getaddr.sin_addr), ntohs(getaddr.sin_port), youcilent.text); if(strcmp(youcilent.text, ".quit") == 0) { break; } } close(sockid); } int main(void) { pthread_t Send; pthread_t Recv; pthread_create(&Send, NULL, pthreadSend, NULL); pthread_create(&Recv, NULL, pthreadRecv, NULL); pthread_join(Send, NULL); pthread_join(Recv, NULL); return 0; }使用线程实现并行收发
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