websocket协议实现验证码

    常见的验证码功能走的都是http协议，点击一下验证码图片里，图片的src指向一个server端地址，而server端返回的数据为二进制图片文件，这样，验证码图片便生成了并点击一下变化一下了。

    websocket协议不太一样，它的返回值并不支持二进制文件，只能传输字符串。但前端其实支持dataUrl,格式类似于<img src="data:image/gif;base64,xxxxxxxxxxxxxxx"> xxxxx为base64位的字符串。所以，可以换个思路在ws协议下也实现验证码功能——在server端将二进制文件编码为base64位的字符串，返回给客户端，客户端将字符串填进img的src属性里，即可实现验证码功能。

python版server端代码大概如下：

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#coding=utf-8

import Image,ImageDraw,ImageFont,cStringIO,base64,random

'''验证码管理器'''

__CODE_COUNT = 4

def createVerificationCode():

    allCode = ["0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"]

    code = ""

    for i in xrange(__CODE_COUNT):

        code += random.choice(allCode) 

    return code

def getImageBase64Data(code):

    text = code

    im = Image.new("RGB",(70,25),(0,0,0))

    dw = ImageDraw.Draw(im)

    dw.text((5,0),text,fill="green",font=ImageFont.truetype('/usr/share/fonts/truetype/freefont/FreeSansOblique.ttf',20))

    buf = cStringIO.StringIO()

    im.save(buf,"gif")

    return base64.b64encode(buf.getvalue())

if __name__ == "__main__"     verificationCode = createVerificationCode()     imageBase64Data =  getImageBase64Data(verificationCode)     socket.send(imageBase64Data)
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客户端如下：
img.src = "data:image/gif;base64,"+ data.imageBase64Data;

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