rtsp工作随记

    最近工作需要，研究了下rtsp协议的传输方式，当然了现在只是入门，以后会陆续添加工作中的所学。
    rtsp是通过socket通信从而与rtsp流服务器就行数据交互的，详细的下一次在记录。借这次机会顺便研究了下unix网络编程，特此在这记录自己的一个小小的网络编程例子......
1 .   server.c

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <strings.h>
#include <stdlib.h>
#include <arpa/inet.h>
int main(int argc,char **argv)
{
    struct sockaddr_in sevAddr;
    struct sockaddr_in cliAddr;
    struct sockaddr_in copyAddr;
//以上三个sockaddr_in结构体代表的IPV4协议簇,
    bzero(&sevAddr,sizeof(sevAddr));
//bzero是专门设计的一个对给定结构体中的元素置0的接口，类似于初始化
    sevAddr.sin_family = AF_INET;  //AF_INET代表的是传输协议是tcp,udp,etc
    sevAddr.sin_addr.s_addr = inet_addr("192.168.0.114");//inet_addr函数是将字符串转换成网络字节序的ip地址格式
//对于IP地址的设定还可以不用固定的ip绑定，而让操作系统自己去找，这部分以后在说
    sevAddr.sin_port = htons(36988);
//以上三个是对server机器的地址端口号设定
//这里注意到了htons（）这个函数，作用是把本地字节序的数据转成网络字节序
//htons，htonl，ntohs，ntohl这几个函数，前两个是本地转网络，后两个是网络转本地
//s和l分别代表了short和long，所以可以注意到端口号用的是s，ip地址用的是l
    int sev_fd,cli_fd;
    int resault;
    pid_t childPid;
    socklen_t cliAddrSize = sizeof(cliAddr);
    sev_fd = socket(AF_INET,SOCK_STREAM,0);   //创建套接字，这里注意到AF_INET和SOCK_STREAM搭配，这表示用的是IPV4的传输协议
    if(-1 == sev_fd)
    {
        printf("socket set up fail,please check it\n");
        return 0;
    }
    resault = bind(sev_fd,(const struct sockaddr*)(&sevAddr),sizeof(sevAddr)); //绑定套接字到本机地址
    if(-1 == resault)
    {
        printf("bind socket error ,please check it\n");
        return 0;
    }
    socklen_t copyAddrSize = sizeof(copyAddr);
    resault = getsockname(sev_fd,(struct sockaddr*)(&copyAddr),&copyAddrSize);//getsockname可以获取绑定在套接字上的地址信息
    if(-1 == resault)
    {
        printf("get sockaddr info error\n");
    }
    printf("port is %u\n",ntohs(copyAddr.sin_port));
    printf("ip is %u\n",ntohl(copyAddr.sin_addr.s_addr));
    resault = listen(sev_fd,3);  //监听改服务器套接字，看有否有客户端链接上来
    if(-1 == resault)
    {
        printf("listen the socket fail,please check it\n");
        return 0;
    }

    while(1)
    {
        cli_fd = accept(sev_fd,(struct sockaddr*)(&cliAddr),&(cliAddrSize));  //接受客户端的请求，这个接口可以顺便获得client的套接字，地址信息，端口号信息等等
        if(-1 == cli_fd)
        {
            printf("accept client connect error,please check it\n");
        }
        if((childPid = fork()) == 0)   //构建子进程为了实现并发服务器的作用
        {
            close(sev_fd);    //关闭监听套接字
            printf("client ip is %u\n",ntohl(cliAddr.sin_addr.s_addr));
            printf("client port is %u\n",ntohs(cliAddr.sin_port));
            int i =0;
            for(;i<10;i++)
            {
                printf(".\n");
                sleep(1);
            }
            exit(0);
        }
        close(cli_fd);  //关闭客户端套接字
    }
}

简单了来说，server的流程其实就是：套接字创建->绑定套接字到指定地址->接听套接字->接受客户端的请求
详细的专业术语这里就不多说了,关键的部分在代码中都做了注释.

2.  client

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <strings.h>
#include <stdlib.h>
#include <arpa/inet.h>

int main(int argc ,char **argv)
{
    if(argc < 2)
    {
        printf("the argv is not enough\n");
        return 0;
    }
    int cli_fd;
    struct sockaddr_in sevaddr;
    sevaddr.sin_family = AF_INET;
    sevaddr.sin_port = htons(36988);
    sevaddr.sin_addr.s_addr = inet_addr(argv[1]);
//以上设置server地址信息
    cli_fd = socket(AF_INET,SOCK_STREAM,0);
    if(-1 == cli_fd)
    {
        printf("client socket set up fail,please check it\n");
        return 0;
    }
    int resault;
    resault = connect(cli_fd,(struct sockaddr*)(&sevaddr),sizeof(sevaddr));   //链接服务器
    if(-1 == resault)
    {
        printf("connect the server fail,please check it\n");
        return 0;
    }
    return 0;
}

client就相对简单了：建立套接字->链接服务器

   接下来说一说INADDR_ANY这个参数的作用，在设定主机服务器ip地址的时候，不同过绑定指定ip的话可以用这个方法来绑定，这个参数的意思就是说任何服务器所带的ip地址接受到的数据都由这个服务器程序来接管。为什么这么说呢？因为很多时候可能服务器有不止一个网卡，那这么一来服务器就有多个IP，所以只要是发到这个服务器上的ip的数据，程序就都能截获了！

   今天研究了下网络编程中的IO口复用技术，特此总结下：
    先上代码：
1. server:

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <strings.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <string.h>
int main(int argc,char **argv)
{
    struct sockaddr_in sevAddr;
    struct sockaddr_in cliAddr;
    struct sockaddr_in copyAddr;
    bzero(&sevAddr,sizeof(sevAddr));
    sevAddr.sin_family = AF_INET;
    //sevAddr.sin_addr.s_addr = inet_addr("192.168.0.114");
    sevAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    sevAddr.sin_port = htons(36988);
    int sev_fd,cli_fd;
    int resault;
    pid_t childPid;
    socklen_t cliAddrSize = sizeof(cliAddr);
    sev_fd = socket(AF_INET,SOCK_STREAM,0);
    if(-1 == sev_fd)
    {
        printf("socket set up fail,please check it\n");
        return 0;
    }
    resault = bind(sev_fd,(const struct sockaddr*)(&sevAddr),sizeof(sevAddr));
    if(-1 == resault)
    {
        printf("bind socket error ,please check it\n");
        return 0;
    }
    socklen_t copyAddrSize = sizeof(copyAddr);
    resault = getsockname(sev_fd,(struct sockaddr*)(&copyAddr),&copyAddrSize);
    if(-1 == resault)
    {
        printf("get sockaddr info error\n");
    }
    printf("port is %u\n",ntohs(copyAddr.sin_port));
    printf("ip is %u\n",ntohl(copyAddr.sin_addr.s_addr));
    resault = listen(sev_fd,3);
    if(-1 == resault)
    {
        printf("listen the socket fail,please check it\n");
        return 0;
    }

    //设置IO复用的select参数属性
    fd_set readSet;
    struct timeval waitTime;
    waitTime.tv_sec = 2;
    waitTime.tv_usec = 0;
    int client[FD_SETSIZE];
    int i;
    char recvbuf[100];
    int maxi = -1;  //记录在client[]中的客户端描述符数
    for(i = 0;i<FD_SETSIZE;i++)
    {
        client[i] = -1;
    }
    FD_SET(sev_fd,&readSet);
    int maxfd = sev_fd;   //监听的描述符的最大数
    printf("the first maxfd is %d\n",sev_fd);
    ////////////////////////////////////////
    while(1)
    {
        waitTime.tv_sec = 2;
        waitTime.tv_usec = 0;
        FD_SET(sev_fd,&readSet);
        maxfd = sev_fd;
        for(i=0;i<FD_SETSIZE;i++)
        {
            if(client[i]!= -1)
            {
                FD_SET(client[i],&readSet);
                maxi = (i+1);
                if(client[i] > maxfd)
                {
                    maxfd = client[i];
                }
            }
        }

        switch(select(maxfd+1,&readSet,NULL,NULL,&waitTime))
        {
            case -1:
                {
                    printf("set select error,please check it\n");
                    return 0;
                }break;
            case 0:
                {
                    printf("no client start to read\n");
                }break;
            default:
                {
                    if(FD_ISSET(sev_fd,&readSet))
                    {
                        //有新的客户端需要连接
                        cli_fd = accept(sev_fd,(struct sockaddr*)(&cliAddr),&(cliAddrSize));
                        if(-1 == cli_fd)
                        {
                            printf("accept client connect error,please check it\n");
                            return 0;
                        }
                        printf("cli_fd is %d\n",cli_fd);
                        for( i = 0;i<FD_SETSIZE;i++)
                        {
                            if(client[i] == -1)
                            {
                                client[i] = cli_fd;
                                maxi = (i+1);
                                if(client[i] > maxfd)
                                {
                                    maxfd = client[i];
                                }
                                break;
                            }
                        }
                        FD_SET(cli_fd,&readSet);
                    }
                    for(i=0;i<maxi;i++)
                    {
                        if(client[i] < -1)
                        {
                            //printf("no client is perpaer for the readn\n");
                            continue;
                        }
                        if(FD_ISSET(client[i],&readSet))
                        {
                            memset(recvbuf,0,sizeof(recvbuf));
                            printf("I have a client : %d\n",client[i]);
                            recvfrom(client[i],recvbuf,sizeof(recvbuf),0,NULL,NULL);
                            printf("recv the message from client is %s\n",recvbuf);
                            close(client[i]);
                            FD_CLR(client[i],&readSet);
                            client[i]=-1;
                            //对客户端描述符的读操作
                        }

                }
        }
        /*
        resault = select(maxfd+1,&readSet,NULL,NULL,&waitTime);
        if(-1 == resault)
        {
            printf("set select error,please check it\n");
            return 0;
        }
        if( 0 == resault)
        {
            //printf("no client has start read\n");
            continue;
        }
        printf("select resault is %d.................\n",resault);
        if(FD_ISSET(sev_fd,&readSet))
        {
            //有新的客户端需要连接
            cli_fd = accept(sev_fd,(struct sockaddr*)(&cliAddr),&(cliAddrSize));
            if(-1 == cli_fd)
            {
                printf("accept client connect error,please check it\n");
                return 0;
            }
            printf("cli_fd is %d\n",cli_fd);
            for( i = 0;i<FD_SETSIZE;i++)
            {
                if(client[i] == -1)
                {
                    client[i] = cli_fd;
                       maxi = (i+1);
                    if(client[i] > maxfd)
                    {
                        maxfd = client[i];
                    }
                    break;
                }
            }
            FD_SET(cli_fd,&readSet);
        }
        for(i=0;i<maxi;i++)
        {
            if(client[i] < -1)
            {
                //printf("no client is perpaer for the readn\n");
                continue;
            }
            if(FD_ISSET(client[i],&readSet))
            {
                memset(recvbuf,0,sizeof(recvbuf));
                printf("I have a client : %d\n",client[i]);
                recvfrom(client[i],recvbuf,sizeof(recvbuf),0,NULL,NULL);
                printf("recv the message from client is %s\n",recvbuf);
                close(client[i]);
                FD_CLR(client[i],&readSet);
                client[i]=-1;
                //对客户端描述符的读操作
            }
        }
        */
        }
    }
}