【導讀】新的系統(tǒng)漏洞層出不窮。黑客或者計算機病毒要想順利滲透入目標計算機中,不。管使用何種技術(shù)手段,必然要尋找目標計算機的漏洞為自己打開入侵的大門。測出網(wǎng)絡(luò)中計算機及防火墻開放的和未開放的端口。種主動防御策略實現(xiàn)的重要技術(shù)手段。本課題通過端口掃描器的研究來提高對計算機安全的認識。用C#語言開發(fā)，在VC編譯環(huán)境下通過測試。的連接，如果目標主機該端口有回復，則說明該端口開放。了對一目標IP進行設(shè)定數(shù)目的端口掃描，對多IP段的特定端口進行掃描。還利用委托技術(shù)實現(xiàn)對界面元素的刷新。

　　

【正文】 ny means, however risky, is very strong. They may work as farmers for ?00 a year less than they39。d be paid for a single horn. A merchant will sell it to consumers for ?5,000 and upwards. More slides followed. A chimpanzee. Valued at ?,300 on the black market. Much in demand for biomedical research, travelling acts, photography, tourist attractions and the television and film industries. A hyacinth macaw. Going price ?,500 to an avid collector. A peregrine falcon. Bought by Arab falconers for ?,000 each. Seeing the peregrine, Gary fot everything else. His favourite bird! It could swoop at over tw o hundred miles an hour, spot its prey more than five miles away. Peregrines had once nearly died out in Britain through eating pigeons which had fed on grain sprayed with pesticides ... Bellingham39。s voice broke into the boy39。s reverie. He was talking about Amazon dolphins. These gentle creatures, already threatened by pollution and riverdamming schemes, were being killedtheir eyeballs sold as ornaments and lucky charms in cities such as Rio de Janeiro. Gary grunted disgustedly, and Susan39。s face showed her feelings. The naturalist then mentioned another charming practice: eating bear paws. Considered a delicacy in Japan, Taiwan, Hong Kong and Singapore, the paws of hunted bears are imported from China. The wildlife trade is a worldwide business, w orth billions of pounds. There are strict rules to control that trade. However, some countries don39。t agree to them. Others say they do, but allow croo ks and cheats to get away with murderanimal murder. That39。s just one of the reasons why The Eden Mission is a top priority ... Bellingham glanced quickly at his watch. I see time is running out. A few final words. Sea Shepherd39。s programme includes try ing to save grey whales and sea otters from oil pollution off California。 manatees from being chopped up by speedboat propellers in Florida39。s waterways。 Amazon dolphins from extermination. We have other tasks too, which I can39。t go into now. The six youngsters sailing with Sea Shepherd, all keen conservationists, will make a valuable contribution. But they39。ll also have to continue the ir school studies ... Someone in the audience groaned. Ben grinned broadly. Thank you for listening, ladies and gentlemen. Wish us luck! Loud applause. Then he answered lastminute questions from journalists. The audienceclad once more in raincoats, and clutching umbrellasbegan to file out. Parents hugged their children, whom they wouldn39。t see again for twelve months, and gave good advice that would probably be fotten or ignored. There were some tears. Neither Gary39。s nor Susan39。s parents were present. They had already said their goodbyes at home and were glad to be spared emotional partings aboard Sea Shepherd. By now the lecture hall was empty except for six young people, eyeing each other somewhat warily, and the three teachers responsible for daily lessons. Bellingham greeted them. Wele to the team. I know we39。re going to get along fine ... His next words were drowned by a sudden blast from Sea Shepherd39。s horn. Almost imperceptibly the ship started to move. Ben39。s steady gaze rested on the group. Well ... this is it. 2. Shipmates After the lecture, a tall, ferretfaced man had pushed people aside to be first down the gangway. He didn39。t look like someone much concerned with conservation. He wasn39。t. Sploshing through puddles, he hurried to a phone box on the quay. He dialled a number. His boss would find the report very interesting. Waving parents watched Sea Shepherd glide away between lines of moored vessels, like a guard of honour. Her bright white hull shone luminously against sea and sky, both the same shade of grey. The teeming rain had stopped. Leaning on the ship39。sr pupil. But Vanessa did well too. When the English lesson came it was Susan39。s turn to shine. She warmed a little to Miss Mimpriss after her praise. Peter Stokes, a dominoes fanatic, taught maths. Norman proved brilliant at the subject. A real genius, Gary thought admiringly. Then geography and history master Geoffrey Baggalley took over. He had once been a physical training instructor and it showed. As he talked, he walked up and down and waved his arms as if doing exercises. Mr. Baggalley caught Susan giggling, but Gary put him in a good mood again by answering all the geography questions correctly. At lunch the unsupervised teenagers were rather noisy, cracking jokes about their teachers. It was harmless fun among newfound friends. Only Darren remained remote, cut off from the lively talk. N ow and then Susan glanced in his direction. He seemed unhappy rather than disgruntled, and she felt sorry for him. Once, their eyes met. Susan couldn39。t be sure, but she thought she saw a slight response before he looked down. A quick breath of fresh air, then the youngsters returned to the lecture hall. Ben Bellingham was waiting for them. Please take your seats in the front row. OK, who cares about conservation? Hands up. Everybody reacted. Bellingham pointed to Vanessa. Why? he demanded. Vanessa opened her mouth in surprise. Er ... The naturalist repeated his question, more gently. Why, Vanessa? Why should you care what happens in Africa, the Amazon, the Antarctic or anywhere else that isn39。t your home? What39。s it got to do with you? He nodded encouragingly. Well? Vanessa stuc k out her chin. Animals have as much right to be on earth as we have. Morethey were here first. And if we39。re the most intelligent creatures, the only ones that are moral, it39。s our duty to look after the environment. Besides, nobody owns the world. All living things are part of nature. So in a way nature owns us ... Blushing, Vanessa tailed off. Wi