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#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#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#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