N Kings You have to place the N kings in on N squared chess board so that no two kings are in same row and column and do not attack each other. About input, first line of the input is number of testcases T. Then every next 2 lines are for the testcase. In the… Continue reading Algorithm – N Kings
I created a web crawler using python and its modules. It follows certain conditions like it reads robots.txt before crawling a page. If the robots.txt allows the page to be crawled the spidey crawls it. It dives in recursively. But there are certain limitations I have set. It do not go beyond 20 pages, as… Continue reading Spidey: Python Web Crawler
Referring to previous post, we will continue with same code. In this post we will try to handle multiple clients. Multiple clients means that multiple client programs can connect to server program. For this we will use threads. Threads are nothing but process and runs only the part that is required (we decide what is… Continue reading Socket Programming: Handling multiclients
We will be understanding the basics of socket programming using Python.You may be thinking why socket programming? Well, its because if you need to send data over a network you need to know about socket. The HTTP websites runs on port 80. Each website has a IP adress. So when you request for a website actually your browser is trying to get data from someipaddress:80. 80 is default port that browser uses, otherwise specified. You might have used Apache. What it does it creates server(we call apache server) and binds it to 127.0.0.1 and port 80. 127.0.0.1 is called loopback address as it tells the browser to look in the consumer’s computer only instead of searching web.
#!/usr/bin/python # Import all from module socket from socket import * # Defining server address and port host = '' #'localhost' or '127.0.0.1' or '' are all same port = 52000 #Use port > 1024, below it all are reserved #Creating socket object sock = socket() #Binding socket to a address. bind() takes tuple of host and port. sock.bind((host, port)) #Listening at the address sock.listen(5) #5 denotes the number of clients can queue #Accepting incoming connections conn, addr = sock.accept() #Sending message to connected client conn.send('Hi! I am server') #send only takes string #Receiving from client data = conn.recv(1024) # 1024 stands for bytes of data to be received print data #Closing connections conn.close() sock.close()
#!usr/bin/python from socket import * host = 'localhost' # '127.0.0.1' can also be used port = 52000 sock = socket() #Connecting to socket sock.connect((host, port)) #connect takes tuple of host and port data = sock.recv(1024) print data sock.send('HI! I am client.') sock.close()
- The program above is waiting for type of programming. Look at the send and recv part in both programming, if server is sending something client must always know when server will send and vice versa or it should wait for that. Of course if you don’t want to drop anything you are sending.
- # is used for comments except the first line it is for telling where python program is. Use path to python.exe on Windows.
- Always use sock.close() to close the socket otherwise socket is in use error will be thrown by python. You may also see it if the program terminates in between.
- 5 in sock.listen is of no use right now as the server.py will terminate as soon as it is done with first client.
- sock.recv() waits till it does not receive something.
- print data will not work with python 3.0+. Use print(data).