socket connect成功后，从新连网后数据发着发着socket就不通了

[xueyu人生]

问题场景：在有网下执行以下程序，数据收发正常，在数据收发过程中直接拔掉网线，等个两分钟，在插上网线，从新创建socket后偶发性的出现数据收发刚开始是正常的，收发几包数据后，socket就不通了，出现“start again rec ”,“rec len -1”日志，然后程序长时间不通的情况下从新创建socket，然后数据收发正常了。

问题：为什么重新插上网线后，数据发着发着，socket就不通了呢？而且write写是成功返回的，ping都是可以通的
有请大神帮忙看下，代码如下，谢谢！

#if 1   
    while(1)
    {
        num = 0;
        recnum = 20;
        socket_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    	if (-1 == socket_fd)
    	{
    		printf("socket_fd create fail\n");
            return;
    	}
        setsockopt(socket_fd,SOL_SOCKET,SO_REUSEADDR,&one,sizeof(one));
        int flags = fcntl(socket_fd,F_GETFL,0);
        fcntl(socket_fd, F_SETFL, flags|O_NONBLOCK);
        int imode =1;
        ioctl(socket_fd,FIONBIO, &imode);
        while((connect(socket_fd, (struct sockaddr *)&g_socket_addr, sizeof(g_socket_addr))) == -1)
        {
            sleep(1);
            if(num++ > 20)
            {   
                printf("num over!\n");
                break;

            }
            printf("connect retry!\n");
        }
        if(num >= 20)
        {
            if(socket_fd > 0)
            {
                close(socket_fd);
                socket_fd = -1;
                continue;
            }

        }
        num = 0;
        printf("connect server 219.144.130.27\n");
        do
        {
            char * send_string = "+123456+";   
        	int len = write(socket_fd, send_string, strlen(send_string));
            printf("write data...\n");
        	if (len <= 0)
        	{
        		printf("send fail \n");
                break;
        	}
            sleep(2);
            memset(data_buf,0,sizeof(data_buf));
            len = recv(socket_fd, data_buf, 15,MSG_NOSIGNAL);
            if(len == -1)   //数据收发异常从这里能看出，断网也是从这里退出
            {
               
               printf("start again rec \n");
               printf("error:%d = <%s>\n",errno,strerror(errno));
               if (write(socket_fd, send_string, strlen(send_string)) <= 0)
            	{
            		printf("write fail \n");
                    break;
            	}
                printf("write data...\n");
            	
               for(;recnum > 0&&(len == -1);recnum--)
               {    
                    sleep(1);
                    memset(data_buf,0,sizeof(data_buf));
                    len = recv(socket_fd, data_buf, 15,MSG_NOSIGNAL);
               }
               if(recnum <= 0)
               {
                    printf("rec len -1\n");
                    break;
               }
               else
               {
                    printf(" rec ok \n");
                    continue;
               }
               
            }
            else
            {
                if(len > 0)
                {
                    printf("rec:%s\n",data_buf);
                }
                else if(len <= 0)
                {
                    printf("len <=0!\n");
                    break;
                }

            }

        }
        while(1);
        close(socket_fd);
        usleep(200*1000);
    }
    #endif

[xueyu人生]

求帮忙解答一哈

[赵4老师]

使用下列函数显示收发的每个字节值，脑查问题：

void HexDump(char *buf,int len,int addr) {
    int i,j,k;
    char binstr[80];

    for (i=0;i<len;i++) {
        if (0==(i%16)) {
            sprintf(binstr,"%08x -",i+addr);
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        } else if (15==(i%16)) {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
            sprintf(binstr,"%s  ",binstr);
            for (j=i-15;j<=i;j++) {
                sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
            }
            printf("%s\n",binstr);
        } else {
            sprintf(binstr,"%s %02x",binstr,(unsigned char)buf[i]);
        }
    }
    if (0!=(i%16)) {
        k=16-(i%16);
        for (j=0;j<k;j++) {
            sprintf(binstr,"%s   ",binstr);
        }
        sprintf(binstr,"%s  ",binstr);
        k=16-k;
        for (j=i-k;j<i;j++) {
            sprintf(binstr,"%s%c",binstr,('!'<buf[j]&&buf[j]<='~')?buf[j]:'.');
        }
        printf("%s\n",binstr);
    }
}