tcp/ip通信第5期之客户机端程序

/*此程序是tcp/ip通信的客户机端程序，
  测试运行在redhat6系统上
  重构readline函数，解决粘包问题——利用“\n”识别一个消息边界
*/
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<arpa/inet.h>
#include<netinet/in.h>
#include<string.h>
#include<signal.h>
#include<errno.h>

#define port 5188

ssize_t readn(int fd, void *buf, size_t count)
{
    size_t nleft = count;//还留下多少字节没有读
    ssize_t nread; //已经读了多少字节
    char *bufp = (char *)buf;
    while (nleft > 0)
            {
                if ((nread = read(fd, bufp, nleft)) < 0)
                {
                    if (errno == EINTR)
 //被信号中断，errno这个全局变量的值就会等于EINTR。
                        continue;
                    return -1;
                }
                else if (nread == 0) //对方关闭或者已经读到eof
                    return count - nleft;
                bufp += nread;
                nleft -= nread;
            }
            return count;
}
     
ssize_t writen(int fd, const void * buf, size_t count) 
{
        size_t nleft = count;
        ssize_t nwritten;
        char *bufp = (char *)buf;
        while (nleft > 0)
            {
                if ((nwritten = write(fd, bufp, nleft)) < 0)
                {
                    if (errno == EINTR)
                        continue;
 //要保证读取的字节数为指定字节数，所以继续
                    return -1;
                }
                else if (nwritten == 0)        
                    continue;
 //由于其他原因引起的什么都没有写进，则继续操作，保证指定字节数
                bufp += nwritten;
                nleft -= nwritten;
            }
            return count;
}

ssize_t recv_peek(int sockfd,void *buf,size_t len)
{
    while(1)
    {
        int ret=recv(sockfd,buf,len,MSG_PEEK);
        if(ret==-1&&errno==EINTR)
            continue;
        return ret;
    }
}

ssize_t recv_line(int sockfd,void *buf,size_t len)
{
    int ret;//记录函数返回值
    int nread;//已经读到的字节数
    char *bufp=buf;
    int nleft=len;
    while(1)
    {
        ret=recv_peek(sockfd,bufp,nleft);
        if(ret<0)
            return ret;
        else if(ret==0)
            return ret;
        nread=ret;
        int i;
        for(i=0;i<nread;i++)
        {
            if(bufp[i]=='\n')
            {
                ret=readn(sockfd,bufp,i+1);
                if(ret!=i+1)
                    exit(1);
                return ret;
            }
        }
        if(nread>nleft)
            exit(1);
        nleft -= nread;
        ret=readn(sockfd,bufp,nread);
        if(ret!=nread)
            exit(0);
        bufp+=nread;
    }
    return -1;
}

int main()
{
    int sock;
    //*****创建套接字*******
    if((sock=socket(PF_INET,SOCK_STREAM,IPPROTO_TCP))<0)
    /*if((listenfd=socket(PF_INET,SOCK_STREAM,0))<0)*/
        perror("error");
        
    //*******ipv4地址结构**********
    struct sockaddr_in servaddr;
    memset(&servaddr,0,sizeof(servaddr)); //清空结构体变量
    servaddr.sin_family=AF_INET;
    servaddr.sin_port= htons(port); //使用端口号：5188
    servaddr.sin_addr.s_addr=inet_addr("192.168.248.129");  //ip地址使用对方的地址，即服务器地址
    printf("the port_id:%d\n",port);
    
    //*********连接请求************
    if(connect(sock,(struct sockaddr*)(&servaddr),sizeof(servaddr))<0)  //使用对方的ip地址
        perror("error");
    else
        printf("connected success.\n");
    
    //************通信过程*************
    char sendbuf[1024]={0};
    char recvbuf[1024]={0};
    while(fgets(sendbuf,sizeof(sendbuf),stdin)!=NULL)
    {
        writen(sock,sendbuf,strlen(sendbuf));
        int ret=recv_line(sock,recvbuf,sizeof(recvbuf));
        if(ret==-1)
            perror("error\n");
        if(ret==0)
        {
            printf("peer is closed.\n");
            break;
        }
        
        fputs(recvbuf,stdout);
        memset(sendbuf,0,sizeof(sendbuf)); //清空缓存
        memset(recvbuf,0,sizeof(recvbuf));
    }
    close(sock);
    return 0;
}