入门Linux系统编程--网络编程

一、网络编程

1、socket服务端代码实现(无连接客户端)

#include 
#include           /* See NOTES */
#include 
//#include 
#include 
#include 
#include 
#include 
 
int main()
{
        int s_fd;
 
        //1.socket
        s_fd = socket(AF_INET,SOCK_STREAM,0);
        if(s_fd == -1){
                perror("socked");
                exit(-1);
        }
 
        struct sockaddr_in s_addr;
        s_addr.sin_family = AF_INET;
        s_addr.sin_port = htons(8989);
        //s_addr.sin_addr.s_addr = "127.0.0.1";  (error)
        inet_aton("192.168.22.148",&s_addr.sin_addr);        //虚拟机linux的ip地址
 
        //2.bind
        bind(s_fd, (struct sockaddr *)&s_addr,sizeof(struct sockaddr_in));
 
        //3.listen
        listen(s_fd,10);
 
        //4.accept
        int c_fd = accept(s_fd,NULL,NULL);
 
        //5.read
 
        //6.write
        printf("connect\n");
        while(1);
 
        return 0;
}

输出结果：

window系统

6、socket服务端代码实现(连接客户端)

#include 
#include           /* See NOTES */
#include 
//#include 
#include 
#include 
#include 
#include 
#include 
 
//int socket(int domain, int type, int protocol);
//int bind(int sockfd, const struct sockaddr *addr,socklen_t addrlen);
 
int main()
{
        int s_fd;
        int n_read;
        char readBuf[128];//定义一个数组
 
        char *msg = "I got your message";
        struct sockaddr_in s_addr;
        struct sockaddr_in c_addr;
 
        memset(&s_addr,0,sizeof(struct sockaddr_in));    //一般来说先清空空间数据，再配置。避免结构体里面有杂乱数据
        memset(&c_addr,0,sizeof(struct sockaddr_in));
 
        //1.socket
        s_fd = socket(AF_INET,SOCK_STREAM,0);
        if(s_fd == -1){
                perror("socked");
                exit(-1);
        }
 
        s_addr.sin_family = AF_INET;
        s_addr.sin_port = htons(8988);
        //s_addr.sin_addr.s_addr = "127.0.0.1";  (不是这样写的)
        inet_aton("192.168.22.148",&s_addr.sin_addr);
 
        //2.bind
        bind(s_fd, (struct sockaddr *)&s_addr,sizeof(struct sockaddr_in));
 
        //3.listen
        listen(s_fd,10);
 
        //4.accept
        int clen = sizeof(struct sockaddr_in);//长度
        int c_fd = accept(s_fd,(struct sockaddr *)&c_addr, &clen);
        
        if(c_fd == -1){
                perror("accept");
        }
        //成功则打印客户端ip地址
        printf("get connect:%s\n",inet_ntoa(c_addr.sin_addr));    //inet_ntoa()函数，把网络格式的 IP 地址转为字符串形式
 
//==================服务端与客户端之间数据交互======================================

        //5.read
        n_read = read(c_fd,readBuf,128);//把客户端的内容读到readBuf
        
        if(n_read == -1){
                perror("read");
        }else{
                printf("get message: %d,%s\n",n_read,readBuf);//打印readBuf中内容
        }
 
        //6.write
        write(c_fd,msg,strlen(msg));//写入操作
 //===============================================================================
        return 0;
}

输出结果：

7、socket客户端代码实现

#include 
#include       
#include 
#include 
#include 
#include 
#include 
#include 



int main()
{
        int c_fd;
        int n_read;
        char readBuf[128];
   
        struct sockaddr_in c_addr;
 
        memset(&c_addr,0,sizeof(struct sockaddr_in));
 
        //1.socket
        c_fd = socket(AF_INET,SOCK_STREAM,0);
        if(c_fd == -1){
                perror("socked");
                exit(-1);
        }
 
        c_addr.sin_family = AF_INET;
        c_addr.sin_port = htons(8988);
        //s_addr.sin_addr.s_addr = "127.0.0.1";  //(不是这样写的)
        inet_aton("192.168.22.148,&c_addr.sin_addr);
 
        //2.connect
        if(connect(c_fd,(struct sockaddr *)&c_addr,sizeof(struct sockaddr_in)) == -1){
                perror("connect");
                exit(-1);            //连接不到服务端会阻塞，出错直接跳出程序，以免搞崩代码
        }
 
        //3.send
        write(c_fd,msg,128);
 
//==================读取服务端的信息===============================
        //4.read
        n_read = read(c_fd,readBuf,128);
        if(n_read == -1){
                perror("read");
        }else{
                printf("get message from server: %d ,%s\n",n_read,readBuf);
        }
//================================================================ 
        return 0;
}

8、实现双方聊天

• server.c

#include 
#include       
#include 
#include 
#include 
#include 
#include 
#include 
 
int main(int argc,char **argv)
{
        int s_fd;
        int c_fd;
        int n_read;
        char readBuf[128];
 
        char *msg = "I got your message";
        struct sockaddr_in s_addr;
        struct sockaddr_in c_addr;
 
        memset(&s_addr,0,sizeof(struct sockaddr_in));
        memset(&c_addr,0,sizeof(struct sockaddr_in));
 
        if(argc != 3){                                //判断一下参数，否则运行参数没写对的时候，出现段错误不知道是哪里搞错。
                printf("param isn't right\n");
        }
 
        //1.socket
        s_fd = socket(AF_INET,SOCK_STREAM,0);
        if(s_fd == -1){
                perror("socked");
                exit(-1);
        }
 
        s_addr.sin_family = AF_INET;
        s_addr.sin_port = htons(atoi(argv[2]));
        //s_addr.sin_addr.s_addr = "127.0.0.1";  (error)
        inet_aton(argv[1],&s_addr.sin_addr);
 
        //2.bind
        bind(s_fd, (struct sockaddr *)&s_addr,sizeof(struct sockaddr_in));
 
        //3.listen
        listen(s_fd,10);
 
        //4.accept
        int clen = sizeof(struct sockaddr_in);
 
        while(1){
                c_fd = accept(s_fd,(struct sockaddr *)&c_addr, &clen);
                if(c_fd == -1){
                        perror("accept");
                }
                printf("get connect:%s\n",inet_ntoa(c_addr.sin_addr));
 
                if(fork() == 0){
                        //5.read
                        n_read = read(c_fd,readBuf,128);
 
                        if(n_read == -1){
                                perror("read");
                        }else{
                                printf("get message: %d ,%s\n",n_read,readBuf);
                        }
 
                        //6.write
                        write(c_fd,msg,strlen(msg));
 
                        break;    //子进程做完一次就退出，父进程继续接收数据
                }
        }
        return 0;
}
~

• client.c

#include 
#include       
#include 
#include 
#include 
#include 
#include 
#include 
 
int main(int argc,char **argv)
{
        int c_fd;
        int n_read;
        char readBuf[128];
 
        char *msg = "from client msg";
        struct sockaddr_in c_addr;
 
        memset(&c_addr,0,sizeof(struct sockaddr_in));
 
        if(argc != 3){                            //判断一下参数，否则参数没写对的时候，出现段错误不知道是哪里搞错。
                printf("param isn't right\n");
        }
 
        //1.socket
        c_fd = socket(AF_INET,SOCK_STREAM,0);
        if(c_fd == -1){
                perror("socket");
                exit(-1);
        }
 
        c_addr.sin_family = AF_INET;
        c_addr.sin_port = htons(atoi(argv[2]));
        //s_addr.sin_addr.s_addr = "127.0.0.1";  (error)
        inet_aton(argv[1],&c_addr.sin_addr);
 
//      memset(&c_addr,0,sizeof(struct sockaddr_in));   (error:清空位置不对)                    
 
        //2.connect
        if(connect(c_fd,(struct sockaddr *)&c_addr,sizeof(struct sockaddr_in)) == -1){
                perror("connect");
                exit(-1);
        }
 
        //3.send
        int n_write = write(c_fd,msg,strlen(msg));
        if(n_write == -1){
                perror("write:");
        }
 
        //4.read
        n_read = read(c_fd,readBuf,128);
        if(n_read == -1){
                perror("read");
        }else{
                printf("get message from server: %d ,%s\n",n_read,readBuf);
        }
        return 0;
}

输出结果：

9、多方消息收发

• server.c

#include 
#include       
#include 
#include 
#include 
#include 
#include 
#include 

      



int main(int argc, char const *argv[])
{
	int mark=0;
	int s_fd;
	int c_fd;
	int n_read;
	int n_write;
	char readBuf[128];
	char returnMsg[128]={0};
	struct sockaddr_in c_addr;
	struct sockaddr_in s_addr;
	memset(&c_addr,0,sizeof(struct sockaddr_in));
	memset(&s_addr,0,sizeof(struct sockaddr_in));//数据清空
	if(argc != 3){
		printf("参数出错\n");
		exit(-1);
	}
	//1.socket  int socket(int domain, int type, int protocol);
	s_fd=socket(AF_INET,SOCK_STREAM,0);
				//ipv4   tcp协议
	if(s_fd == -1){
		printf("创建socket失败");
		perror("socket:");
		exit(-1);

	}
	//2.bind  int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);

	s_addr.sin_family=AF_INET;//ipv4
	s_addr.sin_port=htons(atoi(argv[2]));//端口号，选择5000以上。honts返回网络字节序,atoi(argv[2])防止端口被占用
	//int inet_aton(const char *cp, struct in_addr *inp)
	inet_aton(argv[1],&s_addr.sin_addr);//转换为网络能识别的格式
	bind(s_fd,(struct sockaddr *)&s_addr,sizeof(struct sockaddr_in));

	//3.listen int listen(int sockfd, int backlog);
	listen(s_fd,10);//监听10个连接

	//4.accept int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
	int client=sizeof(struct sockaddr_in);
	while(1){//不断接收客户端
		c_fd=accept(s_fd,(struct sockaddr *)&c_addr,&client);
		if(c_fd == -1){
			printf("连接失败\n");
			perror("accept:");
			exit(-1);

		}
		printf("客户端的ip：%s\n",inet_ntoa(c_addr.sin_addr)); //把网络格式的ip地址打印成字符串格式
		mark++;
		if(fork() == 0){
			if(fork() == 0){
				while(1){
					sprintf(returnMsg,"欢迎第%d号客户端",mark);
					//6.write ssize_t write(int fd, const void *buf, size_t count);
					n_write=write(c_fd,returnMsg,strlen(returnMsg));
					sleep(20);
				}
			}
			while(1){
				//5.read  ssize_t read(int fd, void *buf, size_t count);
				memset(readBuf,0,sizeof(readBuf));
				n_read=read(c_fd,readBuf,128);
				if(n_read == -1){
					perror("read:");
				}else{
					printf("得到%d号的消息:%s\n",mark,readBuf);
				}
			}
			
		}
	}
	return 0;
}

• client.c

#include 
#include       
#include 
#include 
#include 
#include 
#include 
#include 


int main(int argc, char const *argv[])
{

	int c_fd;
	int n_read;
	int n_write;
	int c_connect;
	char readBuf[128];
	char returnMsg[128]={0};
	char *quit="quit";
	struct sockaddr_in c_addr;
	memset(&c_addr,0,sizeof(struct sockaddr_in));//数据清空
	if(argc != 3){
		printf("参数出错\n");
		exit(-1);
	}
	//1.socket  int socket(int domain, int type, int protocol);
	c_fd=socket(AF_INET,SOCK_STREAM,0);
				//ipv4   tcp协议
	if(c_fd == -1){
		printf("创建socket失败");
		perror("socket:");
		exit(-1);

	}
	c_addr.sin_family=AF_INET;//ipv4
	c_addr.sin_port=htons(atoi(argv[2]));//端口号，选择5000以上。honts返回网络字节序
	//int inet_aton(const char *cp, struct in_addr *inp)
	inet_aton(argv[1],&c_addr.sin_addr);//转换为网络能识别的格式
	//2.connect  int connect(int sockfd, const struct sockaddr *addr,socklen_t addrlen);
    c_connect=connect(c_fd,(struct sockaddr *)&c_addr,sizeof(struct sockaddr));
    if(c_connect == -1){
    	printf("连接失败\n");
    	perror("connect:");
    }
	while(1){
		if(fork() == 0){
			while(1){//不断写入
				memset(returnMsg,0,sizeof(returnMsg));
				printf("请输入:\n");
				gets(returnMsg);
				//3.write/send ssize_t write(int fd, const void *buf, size_t count);
				n_write=write(c_fd,returnMsg,strlen(returnMsg));
				if(strcmp(quit,returnMsg) == 0){//如果输入quit则客户端就退出
					
					exit(0);
				
				}
			}
		}
		while(1){//不断读取
			memset(readBuf,0,sizeof(readBuf));//不断清空数据防止数据重复出现
			//4.read  ssize_t read(int fd, void *buf, size_t count);
			n_read=read(c_fd,readBuf,128);
			if(n_read == -1){
				perror("read:");
			}else{
				printf("来自服务端的消息:%s\n",readBuf);
			}
		}
		//5.close     int close(int fd);
		
		close(c_fd);
	}
	return 0;
}

二、往期文章

1、入门Linux系统编程–文件
2、入门Linux系统编程–进程
3、入门Linux系统编程–线程
4、入门Linux系统编程–进程间通信
5、入门Linux系统编程–网络编程