（2）讲解在昨天没有完成的作业内容：图片获取
代码如下：虚拟机部分：server.c

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

void *threadFunc(void *arg)
{
	char cmd[5] = {0};
	char fileHead[100] = {0};
	char fileName[20];
	int fileSize = 0;
	char buf[1024] = {0};
        int fd;
        int connFd = *((int *)arg);
	//recv "pic"
	int ret = recv(connFd, cmd, sizeof(cmd), 0);	
	if(ret < 0)
	{
		perror("recv error!");
		close(connFd);
		return NULL;
	}

	if(0 == strcmp(cmd, "pic"))
	{
		//send fileHead
		strcpy(fileName, "1.png");
		struct stat stBuf = {0};
		stat(fileName, &stBuf);
		fileSize = stBuf.st_size;

		sprintf(fileHead, "%s#%d", fileName, fileSize);
		ret = send(connFd, fileHead, sizeof(fileHead), 0);	
		if(ret < 0)
		{
			perror("send error!");
			close(connFd);
			return NULL;
		}

		//send file

		fd = open(fileName, O_RDONLY);
		if(fd < 0)
		{
			perror("open error!");
			close(connFd);
			return NULL;
		}
		while(1)
		{
			memset(buf, 0, sizeof(buf));
			ret = read(fd, buf, sizeof(buf));
			if(ret < 0)
			{
				perror("read error!");
				close(connFd);
				close(fd);
				return NULL;
			}
			else if(0 == ret)
			{
				break;
			}
			ret = send(connFd, buf, ret, 0);
			if(ret < 0)
			{
				perror("send error!");
				close(connFd);
				close(fd);
				return NULL;
			}
		}
	}
	else
	{
		printf("cmd error!\n");
	}
	close(connFd);
	close(fd);
    pthread_exit(NULL);
}

int main()
{

	//1.socket
	int iServer = socket(AF_INET,SOCK_STREAM,0);
	if(iServer < 0)
	{
		perror("socket");
	}
	printf("socket ok!\n");

	//2.bind
	struct sockaddr_in stServer;
	stServer.sin_family = AF_INET;
	stServer.sin_port = htons(8888);
	stServer.sin_addr.s_addr = inet_addr("192.168.15.15");//inet_addr("192.168.0.103");  
	int ret = bind(iServer,(struct sockaddr *)&stServer,sizeof(stServer));
	if(ret < 0)
	{
		perror("bind");
	}
	printf("bind ok!\n");

	//3.listen
	ret = listen(iServer,5);
	if(ret < 0)
	{
		perror("listen");
	}
	printf("listen ok!\n");


	//4.accept
	struct sockaddr_in stClient;
	socklen_t len = sizeof(stClient);
	while(1)
	{
		printf("wait for a new client\n");
		memset(&stClient,0,sizeof(stClient));
		int iClient = accept(iServer,(struct sockaddr *)&stClient,&len);
		if(iClient < 0)
		{
			perror("accept");
			return -1;
		}
		else
		{
			printf("accept ok!\n");
			pthread_t th1;
			while(pthread_create(&th1,NULL,threadFunc,&iClient) != 0);
			pthread_detach(th1);
		
		}
	}
	//7.close
	close(iServer);
	return 0;
}

qt客户端：

#include "widget.h"
#include "ui_widget.h"
#include <QHostAddress>
#include <QDebug>
#include "qpalette.h"

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    QPalette pal = palette();
    pal.setColor(QPalette::Background, QColor(0x00,0xff,0x00,0x00));
    setPalette(pal);

    socket = new QTcpSocket(this);

    connect(socket, SIGNAL(connected()),this,SLOT(connectedSlot()));

    ui->getPicBtn->setEnabled(false);

    connect(socket,SIGNAL(readyRead()),this,SLOT(recvDataSlot()));

    connect(socket,SIGNAL(disconnected()),this,SLOT(disConnectedSlot()));

    flag = true;
}

Widget::~Widget()
{
    delete ui;
}

void Widget::on_connBtn_clicked()
{
    socket->connectToHost(QHostAddress("192.168.15.15"),8888);
}

void Widget::connectedSlot()
{
    ui->connBtn->setEnabled(false);
    ui->getPicBtn->setEnabled(true);
}

void Widget::on_getPicBtn_clicked()
{
     char cmd[5] = "pic";
     socket->write(cmd, sizeof(cmd));
}

void Widget::recvDataSlot()
{
    qDebug() << "********";
    if(true == flag)
    {
        char fileHead[100] = {0};
        //接收文件头
        socket->read(fileHead, sizeof(fileHead));
        //解析文件头
        QString str(fileHead);
        fileName = str.section('#', 0,0);
        fileSize = str.section('#',1,1).toInt();
        flag = false;
        arr.clear();
    }
    else
    {
        //只要flag不等于true，哪怕这个被调用很多次，也只会进入到这个分支
        QByteArray arrTmp = socket->readAll();
        arr.append(arrTmp);
        if(arr.size() >= fileSize)
        {
            //将文件显示在label上
            flag = true;
            QPixmap pix;
            //将arr中的文件内容直接显示
            bool ok = pix.loadFromData(arr);
            if(true == ok)
            {
               qDebug() << "load pic ok";
               ui->label->setPixmap(pix);
               ui->label->setScaledContents(true);
            }
        }
    }

}

void Widget::disConnectedSlot()
{
    ui->connBtn->setEnabled(true);
    ui->getPicBtn->setEnabled(false);
}

//头文件：widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QTcpSocket>

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

private slots:
    void on_connBtn_clicked();
    void connectedSlot();

    void on_getPicBtn_clicked();
    void recvDataSlot();
    void disConnectedSlot();

private:
    Ui::Widget *ui;
    QTcpSocket *socket;
    bool flag;
    QString fileName;
    int fileSize;
    QByteArray arr;
};

#endif // WIDGET_H

效果如图;