CODEWITHSUNDEEP
rubysockets
Practical1
Practical1

Reputation: 678

What does "line = s.gets" mean in this socket example?

require 'socket'

s = TCPSocket.new('localhost', 2000)

while line = s.gets # Read lines from socket
  puts line         # and print them
end

s.close             # close socket when done

I'm a newcomer to Ruby and sockets in general; I got this code from the Ruby Sockets documentation page as one of their examples. I understand everything except the line = s.gets snippet. When gets is called is it getting input or is a method of the class Socket? Can anyone please give me an explanation? Thanks!

Upvotes: 0

Views: 401

Answers (2)

Ilya Konyukhov
Ilya Konyukhov

Reputation: 2791

The example from documentation can be explained as

Open a TCP socket to localhost, port 2000.

Read from it line by line; while reading print what was read.

When there is no content left to read, close the socket.

Basically, I think the whole expression

while line = s.gets
  puts line
end

can be confusing for Ruby newcomers.

The code snippet above reads content from socket s with method gets. This method returns a "line" (a string), including trailing symbol \n. That result is assigned to line variable.

line = s.gets expression is not a comparison as it may seem; it's assignment. Every assignment in Ruby returns a value, which is assigned. So the result of this operation is a string, returned by gets.

When evaluated by while statement, string is converted to boolean. Any string, even empty one, is considered as true, so block with puts line is executed.

Since it is a while loop, it will be repeated again and again, until gets method returns nil, which means there is nothing left to read from the socket (transfer complete).

Upvotes: 2

wehdi
wehdi

Reputation: 96

s = TCPSocket.new 'localhost', 2000 # Opens a TCP connection to host


while line = s.gets # Read the socket like you read any IO object.
                    # If s.gets is nil the while loop is broken
      puts line     # Print the object (String or Hash or an object ...)
end

Its like :

Client side

#Init connection
   Client.send("Hello") #The client send the message over socket(TCP/IP)
#Close connection

Server side

#Init connection
    while line = s.gets # The client get the message sended by the client and store it in the variable line

        puts line  # => Hello
    end
#Close connection

Upvotes: 1

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