1. 协议
通信双方约定的一套标准成为协议
2. 国际网络协议标准
2.1 OSI七层模型(理论模型)
应用层:传输的数据(a.out)
表示层:数据是否加密
会话层:是否需要建立会话链接(网络断开连接状态)
传输层:传输数据的方式(TCP、UDP)
网络层:数据路由(IP地址)
数据链路层:局域网内的数据传输(交换机局域网内多设备的链接)
物理层:物理介质链接(网线、电缆 硬件高低电平)
2.2 TCP/IP网络协议模型(实际开发)
应用层
传输层
网络层
网络接口层(链路+物理)
1. 应用层协议
FTP TFTP HTTP SMTP TELNET
2. 传输层协议——UDP、TCP
UDP:用户数据报协议(无连接)
特点:
1.不安全、不可靠
2.数据量小
3.占用资源开销小
TCP:传输控制协议(有链接)
特点:
1.安全、可靠
2.数据量大
3.占用资源开销大
三次握手建立链接
数据传输过程中双方通过序列号和确认号保障数据传输完整性
四次挥手结束链接
3. 网络层协议——局域网
3.1 IPv4
(1)IP:192.168.0.189 —— 网络位(192.198.0) 主机位(189)
IP地址 = 网络位 + 主机位
网络位:IP地址所在的网段
主机位:在局域网内的主机编号
(2)子网掩码:搭配IP地址使用,区分IP地址中的网络位和主机位
子网掩码是1的部分对应IP地址网络位
子网掩码是0的部分对应IP地址主机位
(3)网段号:网络位不变,主机位全为0的IP地址——192.168.0.0
广播号:网络位不变,主机位全为1的IP地址——192.168.0.255
(给广播号发送一个信息,所有的IP地址都能搜到)
(4)IP地址的分类
A类:1.0.0.0 - 126.255.255.255
子网掩码:255.0.0.0
管理大规模网络
私有IP:10.0.0.0 - 10.255.255.255
B类:128.0.0.0 - 191.255.255.255
子网掩码:255.255.0.0
管理大中规模网络
私有IP:172.16.0.0 - 172.31.255.255
C类:192.0.0.0 - 223.255.255.255
子网掩码:255.255.255.0
管理中小规模网络
私有IP:192.168.0.0 - 192.168.255.255
D类:224.0.0.0 - 239.255.255.255
用于组播传输(给一组人传输数据)
E类:240.0.0.0 - 255.255.255.254
用于科研实验
公有IP地址:能够直接上网的IP地址(路由器)
私有IP地址:不能直接上网的IP地址(个人主机)
(5)MAC地址:网卡地址 物理地址(此地址不会重复,是唯一的)
(6)端口号:唯一识别同一主机不同进程的号码
(0 - 65535)(不要使用10000以内的,10000以内的是系统的)
(7)注意
IP地址是为了找某一个网段、MAC地址是为了找在局域网中找到某一个主机
4. UDP编程——不论对方是否收到都能完成发送
4.1 socket
int socket(int domain, int type, int protocol);
功能:
创建一个用来进程通信的套接字,返回文件描述符
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
返回值:
成功返回套接字新文件描述符
失败返回-1
4.2 sendto
ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
const struct sockaddr *dest_addr, socklen_t addrlen);
功能:
给另一个套接字发送消息
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
返回值:
成功返回发送字节个数
失败返回-1
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 */
};
4.3 inet_addr
in_addr_t inet_addr(const char *cp);
功能:
将字符串IP地址转换为二进制IP地址
参数:
cp:字符串IP地址空间首地址
返回值:
成功返回二进制IP地址
4.4 htons
uint16_t htons(uint16_t hostshort);
功能:
将本地字节序(小端)转换为网络字节序(大端)
参数:
hostshort:本地端口号
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)
4.5 bind
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);
功能:
将套接字与IP地址端口绑定在一起
参数:
sockfd:文件描述符
addr:结构体空间首地址
addrlen:信息的长度
返回值:
成功返回0
失败返回-1
4.6 recvfrom
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,
struct sockaddr *src_addr, socklen_t *addrlen);
功能:
接收数据
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
返回值:
成功返回实际接收字节数
失败返回-1
注意:
该函数具有阻塞功能
4.7 UDP编程示例代
(1)单方向收发
1. 头文件
#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)
#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 = inet_addr("192.168.0.155");
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;
}
3. 接收端代码(recv.c)
#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 = inet_addr("192.168.0.155");
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)双向通信
1. 头文件
#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
#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 = inet_addr("192.168.0.155");
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;
}
3. 接收端
#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 = inet_addr("192.168.0.155");
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;
}
(3)使用UDP进行文件复制(cp)
1. 服务端
#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;
}
2. 客户端
#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 = inet_addr("192.168.203.128");
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;
}
(4) 使用UDP进行两端聊天(chat)
1. 服务端
#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 = inet_addr("127.0.0.1");
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;
}
2. 客户端
#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 = inet_addr("127.0.0.1"); 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;
}