clientNet.py

import socket
##Buffers
writingbuffer = bytearray()
readingbuffer = bytearray()

## Connect non-blocking to the given server with ip and port 
def tcp_connect(ip,port):
    server_socket = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    server_socket.connect((ip,port))
    server_socket.setblocking(0)
    return server_socket
    
### Writing functions ###
def clearbuffer():
    global writingbuffer
    writingbuffer = bytearray(0)
    writebyte()
    writebyte()
## Write 1 byte to the writing buffer
def writebyte(byte=0):
    global writingbuffer
    writingbuffer.append(byte)
## Write a 2-byte short to the writing buffer
def writeshort(value):
    global writingbuffer
    a = value.to_bytes(2,byteorder='big')
    writingbuffer = writingbuffer + a    

## Write a 4-byte integer to the writing buffer
def writeint(value):
    global writingbuffer
    a = value.to_bytes(4,byteorder='big')
    writingbuffer = writingbuffer + a

## Write a string to the writing buffer
## NOTE the string will end in a null terminating byte(0)
def writestring(text):
    global writingbuffer
    a = bytes(text,encoding='ascii')
    writingbuffer =writingbuffer + a
    writebyte()

## Send the writing buffer to the given socket
def sendmessage(sock):
    global writingbuffer
    size = len(writingbuffer)
    writingbuffer[0] = size - 2
    sock.send(writingbuffer)

### Reading functions ###

## Receive message from given sock
## returns size of message or 0 if no message was received
def receivemessage(sock):
    global readingbuffer
    
    buffer = bytearray(256)
    try:
        nbytes = sock.recv_into(buffer)
        readingbuffer = readingbuffer + buffer[:nbytes]
        #print('messaged received size ' + str(len(readingbuffer)))
    except socket.error as e:
        size = len(readingbuffer)
        ##Read first 2 bytes that dont contain message
        if (size > 2):
            readbyte()
            readbyte()
        return size
    ##Read first 2 bytes
    if (nbytes > 0):
        readbyte()
        readbyte()
    return nbytes

## Read 1 byte from the reading buffer
def readbyte():
    global readingbuffer
    return readingbuffer.pop(0)

## Read a string from the reading buffer
## NOTE readstring creates a string from continously reading bytes
## until it reaches null terminating byte (0)
def readstring():
    char = readbyte()
    word = bytearray()
    while char != 0:
        word.append(char)
        char = readbyte()
    return word.decode('ascii')

## Read a 4 byte integer from the reading buffer
def readint():
    number = bytearray(0)
    for x in range(4):
        number.append(readbyte())
    return int.from_bytes(number,byteorder='little')

## Read a 2 byte integer from the reading buffer
def readshort():
    number = bytearray(0)
    for x in range(2):
        number.append(readbyte())
    return int.from_bytes(number,byteorder='little')

## Print both the reading and writing buffer
## Mainly for debugging
def printbuffer():
    global readingbuffer, writingbuffer
    print ('Reading buffer')
    print (readingbuffer)
    print ('Writing buffer')
    print (writingbuffer)