proxyserver.py

from socket import *
import sys
import re
import os


def createRequest(host, url, originalRequest):
    try:
        hostInd = url.index(host)
        if len(url[hostInd + len(host):]) < 3:
            url = 'http://www.' + url

            pass
        else:
            url = url[hostInd + len(host):]
    except ValueError:
        pass
    httpHeader = "GET " + url + " HTTP/1.1\r\n"
    httpHeader += ("Host: " + host + '\r\n')
    httpHeader += "Connection: close\r\n"
    
    for line in originalRequest.split('\r\n'):
        if 'User-Agent' in line:
            httpHeader += (line + '\r\n')
        if 'Accept:' in line:
            httpHeader += (line + '\r\n')
        if 'Referer:' in line:
            httpHeader += (line + '\r\n')
        if 'Accept-Encoding:' in line:
            httpHeader += (line + '\r\n')
        if 'Accept-Language:' in line:
            httpHeader += (line + '\r\n')
        if 'Cookie:' in line:
            httpHeader += (line + '\r\n')
    httpHeader += '\r\n\r\n'
    return httpHeader

def createResponse(filename, data):
    
    httpHeader = 'HTTP/1.1 200 OK\r\n'
    if '.jpg' in filename:
        httpHeader += 'Content-Type: image/jpeg\r\n'
    elif 'html' or 'htm' in filename:
        httpHeader += 'Content-Type: text/html\r\n'
    elif '.ico' in filename:
        httpHeader += 'Content-Type: image/x-icon\r\n'
    elif '.css' in filename:
        httpHeader += 'Content-Type: text/css\r\n'
    elif '.js' in filename:
        httpHeader += 'Content-Type: application/javascript\r\n'
    elif '.txt' in filename:
        httpHeader += 'Content-Type: text/plain\r\n'
    else:
        httpHeader += 'Content-Type: application/octet-stream\r\n'
    httpHeader += ('Content-Length: ' + str(len(data)))
    # Double space between header and data
    httpHeader += '\r\n\r\n'
    print 'RESPONSE HEADER FROM PROXY TO CLIENT'
    print httpHeader
    print 'END OF HEADER\n'
    httpHeader += data
    return httpHeader

def create404(data):
    httpHeader = 'HTTP/1.1 404 Not Found\r\n'
    httpHeader += 'Content-Type: text/html; charset=UTF-8\r\n'
    print 'RESPONSE HEADER FROM PROXY TO CLIENT'
    print httpHeader
    print 'END OF HEADER\n'
    httpHeader += '\r\n\r\n'
    httpHeader += data
    return httpHeader

if len(sys.argv) <= 1:
  print 'Usage : "python proxyserver.py server_ip"\n[server_ip : Address of the proxy server'
  sys.exit(2)

serverIP = sys.argv[1]

# buffer size
BUFFER_SIZE = 1048576

#port number is arbituary
welcomePort = 5005
# holds names of files sent with special encoding i.e gzip
encodeFlag = []
encodeDict = {}

try:
    #create welcoming socket
    welcomeSocket = socket(AF_INET, SOCK_STREAM)

    #bind to the server address
    welcomeSocket.bind((serverIP, welcomePort))

    #begin listening (argument is number of allowed queued connections)
    welcomeSocket.listen(5)


#listening loop
    while True:
        # Start receiving data from client
        print('WEB PROXY SERVER IS LISTENING')
        
        # Accept() returns a new connection socket along with the address
        clientSocket, clientAddress = welcomeSocket.accept()
        print('WEB PROXY SERVER CONNECTED WITH ' + str(clientAddress))

        # wait 100ms second to hear from client
        try:
            clientSocket.settimeout(0.1)
            request = clientSocket.recv(BUFFER_SIZE)
        except timeout:
            clientSocket.shutdown(SHUT_RDWR)
            clientSocket.close()
            continue 
        
        # do not parse empty message
        if(len(request) > 0):
            print('MESSAGE RECEIVED FROM CLIENT:')
            print(request)
            print 'END OF MESSAGE RECEIVED FROM CLIENT' 
        else:
            clientSocket.shutdown(SHUT_RDWR)
            clientSocket.close()
            continue 
        
        # Parse Request Header
        
        method = request.split(" ")[0]
        url = request.split(" ")[1]
       # url = url[1:]
        try:
            domainIndex = url.index('.')
            host = url[:domainIndex+4]
        except ValueError:
            pass
        for line in request.split('\r\n'):
            if "Referer:" in line:
                temp = line.split(" ")[1]
                temp = temp.split(':'.join([str(serverIP), str(welcomePort)]))[1]
                domIndex = temp.find(".")
                host = temp[1:domIndex+4]
        
        print '[PARSE MESSAGE HEADER]:'
        print 'METHOD = ' + method + ', DESTADDRESS = ' + url + ', HTTPVersion = ' + str(request.split()[2])

                
        writefile = True
        # See if the URL contains a filename 
        filematcher = re.compile("((.?)*\.(jpg|htm|html|png|ico|js|css|gif)$)")
        fmatch = filematcher.match(url)
        if (fmatch):
            filename = url.split('/')[-1]
            if filename in os.listdir("."):
                # Cache Hit
                print 'Cache Hit'
                with open(filename, 'r') as file:
                    # Assemble HTTP response 
                    httpHeader = 'HTTP/1.1 200 OK\r\n'
                    if '.jpg' in filename:
                        httpHeader += 'Content-Type: image/jpeg\r\n'
                    elif 'html' or 'htm' in filename:
                        httpHeader += 'Content-Type: text/html\r\n'
                    elif '.ico' in filename:
                        httpHeader += 'Content-Type: image/x-icon\r\n'
                    elif '.css' in filename:
                        httpHeader += 'Content-Type: text/css\r\n'
                    elif '.js' in filename:
                        httpHeader += 'Content-Type: application/javascript\r\n'
                    elif '.txt' in filename:
                        httpHeader += 'Content-Type: text/plain\r\n'
                    else:
                        httpHeader += 'Content-Type: application/octet-stream\r\n'
                    
                    # Reading the whole file until it doesn't work 
                    data = file.read()
                    httpHeader += ('Content-Length: ' + str(len(data)))
                    
                    # See if it was sent using special encoding                    
                    if filename in encodeFlag:
                        httpHeader += (encodeDict[filename] + '\r\n') 
                    
                    # Double space between header and data
                    httpHeader += '\r\n\r\n'
                    
                    print 'HTTP Header sent to Client:'
                    print httpHeader
                    # Add the file data    
                    httpHeader += data
                    
                    # Send 
                    clientSocket.send(httpHeader)
                    clientSocket.close()
                    continue                                        
        else:
            writefile = False
#            if url[0] == '/':
#                url = url[1:]
            #url = "/"
            # if here then the request was not for a specific file (metadata?)

# Cache miss must send request to original destination
        
        try:
            print '[LOOK UP IN CACHE]: NOT FOUND, BUILD REQUEST TO SEND TO ORIGINAL SERVER'
            forwardSocket = socket(AF_INET, SOCK_STREAM)
            # Connect on port 80
            if host[0] == '/':
                host = host[1:]
            host = host
            print '[PARSE REQUEST HEADER] HOSTNAME IS ' + host 
            hostIP = gethostbyname(host)
            address = (hostIP, 80)
            forwardSocket.connect(address)
            newRequest = createRequest(host, url, request)
            print 'REQUEST MESSAGE SENT TO ORIGINAL SERVER:'
            print newRequest
            print 'END OF MESSAGE SENT TO ORIGINAL SERVER.\n'
            forwardSocket.send(newRequest)
            # keep reading and forwarding until nothing server stops
#            count = 0
            error404 = False
            if(writefile):
                with open(filename, 'w') as file:                
                    while True:
                        forwardSocket.settimeout(0.5) # 500ms
                        response = forwardSocket.recv(BUFFER_SIZE)
                        if(len(response) > 0):
                            try:
                                if '404' in response.split('\r\n\r\n')[0]:
                                    temp = response.split('\r\n\r\n')
                                    header = temp[0]
                                    print 'RESPONSE HEADER FROM ORIGINAL SERVER'
                                    print header
                                    print 'END OF HEADER'
                                    if len(temp) < 3:
                                        data = temp[1]
                                    else:
                                        data = '\r\n\r\n'.join(temp[1:])
                                    proxy_response = create404(data)
                                    clientSocket.send(response)
                                    error404 = True
                                    break
                                    
                                if 'HTTP' in response.split('\r\n\r\n')[0]:
                                    temp = response.split('\r\n\r\n')
                                    header = temp[0]
                                    print 'RESPONSE HEADER FROM ORIGINAL SERVER'
                                    print header
                                    print 'END OF HEADER'
                                    print '[WRITE FILE INTO CACHE]: ' + filename +'\n'
                                    if len(temp) < 3:
                                        data = temp[1]
                                    else:
                                        data = '\r\n\r\n'.join(temp[1:])
                                    file.write(data)
                                else:
                                    file.write(response)
                                # See if there is special encoding to note
                                
                                for line in response.split('\r\n'):
                                    if 'Content-Encoding:' in line:
                                        encodeFlag.append(filename)
                                        encodeDict[filename] = line

                            except IndexError:
                                file.write(response)
                                clientSocket.send(response)
                            
                        else:
                           

                            break
            else:
                while True:
                        forwardSocket.settimeout(1.0)
                        response = forwardSocket.recv(BUFFER_SIZE)
    
                        if(len(response) > 0):
                            clientSocket.send(response)
                        else:
                            break
            if error404:
                with open(filename, 'r') as file:
                    data = file.read()
                    proxy_response = create404(data)
                    clientSocket.send(proxy_response)
            else:
                with open(filename, 'r') as file:
                    data = file.read()
                    proxy_response = createResponse(filename, data)
                    clientSocket.send(proxy_response)
            forwardSocket.close()
            clientSocket.close()
        except timeout:
            print 'timeout'
            forwardSocket.close()
            clientSocket.close()
        except Exception as e:
            print(e)
            print("Illegal Request")
       # else:
   #     print('404 Error - File note found')
except KeyboardInterrupt:
    print 'Exiting Gracefully'
    welcomeSocket.shutdown(SHUT_RDWR)
    welcomeSocket.close()
    sys.exit()

    
if __name__ == '__main__':
    main()