vtds.py

# VideoTex Demo Server
#
# by tim lindner
# November 2022

import socket
import random
import time
from PIL import Image
from pathlib import Path
import glob

def sendAll_print(data):
    for char in data:
        if char < 0x20:
            print("out: " + hex(char))
        else:
            print("out: " + hex(char) + " " + chr(char))
    
    conn.sendall(data)          


def calcChecksum(data):
    result = 0
    tc = 0
    
    for char in data[2:]:
        
        if char != 0x10:
            if tc == 1:
                char = char - 0x40
                tc = 0
            
            result = result * 2
            
            if result > 255:
                result = result - 256
                result = result + 1
                
            result = result + char
            
            if result > 255:
                result = result - 256
                result = result + 1
        else:
            tc = 1
    
    if result < 0x40:
        return bytes(chr(0x10)+chr(result+0x40), 'latin_1')

    else:
        return bytes(chr(result), 'latin_1')

HOST = "127.0.0.1"  # Standard loopback interface address (localhost)
PORT = 65432  # Port to listen on (non-privileged ports are > 1023)

print ("Opening listening socket on address:",{HOST},"and port:",{PORT})

with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    conn, addr = s.accept()
    mode = 0
    next_mode = 0
    input = b''
    interrogate = b''
    global_block_number = b'1'
    
    with conn:
        print(f"Connected by {addr}")
        while True:
            # Wait for initial keyboard input
            if mode==0:
                data = conn.recv(1024)
                if not data:
                    break

                if data == b'\r':
                    # send interrogate sequence
                    conn.sendall(b"\x1b\x49")
                    # receive data with no echo
                    next_mode = 7
                    mode = 6;
            
            # Display main menu
            if mode==1:
                if interrogate != "":
                    conn.sendall(b"\r\nTerminal code: ")
                    conn.sendall(interrogate)
                    
                conn.sendall(b"\r\nHere is the main menu:")         
                conn.sendall(b"\r\n1. Print Lorem Ipsum")
                conn.sendall(b"\r\n2. Display semi graphics")
                conn.sendall(b"\r\n3. Display med res graphics")
                conn.sendall(b"\r\n4. Load stored text")
                conn.sendall(b"\r\n5. Load and run executable")
                conn.sendall(b"\r\n6. Log out")
                conn.sendall(b"\r\nChoose: ")
                input = b""
                next_mode = 3
                #Change sursor to red
                #conn.sendall(b"\x1b\x60\xaf")
                mode = 2

            # accept input end with \r then goto next_mode
            if mode==2:
                data = conn.recv(1024)
                if not data:
                    break

                for char in data:
                    if char < 0x20:
                        print("in: " + hex(char))
                    else:
                        print("in: " + hex(char) + " " + chr(char))

                if data == b'\x11':
                    # eat this byte
                    pass
                elif data == b'\r':
                    mode = next_mode
                    conn.sendall(b"\r\n")
                    # change cursor back to blue
                    #conn.sendall(b"\x1b\x60\xbf")
                elif data == b'\b':
                    input = input[:-1]
                    if len(input)>0:
                        conn.sendall(b"\b")
                else:
                    input = input + data;
                    conn.sendall(data)
                    
            # handle main menu selection
            if mode==3:
                if input == b"1":
                    mode = 4
                elif input == b"2":
                    mode = 8
                elif input == b"3":
                    mode = 10
                elif input == b"4":
                    mode = 12
                elif input == b"5":
                    mode = 16
                elif input == b"6":
                    break;
                else:
                    mode = 1
            
            # ask how manu word to print of lorem ipsum
            if mode == 4:
                conn.sendall(b"\r\nHow many words? ")
                input = b""
                next_mode = 5
                mode = 2
            
            if mode == 5:
                fd = Path('lorem.txt').read_text()
                
                count = int(input)
                
                for element in fd:
                    if element == " ":
                        count = count - 1
                    
                    if count == 0:
                        break;
                        
                    conn.sendall(bytes(element,'utf-8'))
            
                conn.sendall(b"\r\nPress <enter> to continue")
                next_mode = 1
                mode = 2
            
            # accept input end with \r (no echo) then goto next_mode
            if mode == 6:
                data = conn.recv(1024)
                if not data:
                    break

                for char in data:
                    if char < 0x20:
                        print("in: " + hex(char))
                    else:
                        print("in: " + hex(char) + " " + chr(char))
    
                if data == b'\x11':
                    pass
                elif data == b'\r':
                    mode = next_mode
                elif data == b'\b':
                    input = input[:-1]
                else:
                    input = input + data;
            
            # save interrogate
            if mode == 7:
                interrogate = input
                mode = 1
            
            # ask how many colored squared to print
            if mode == 8:
                conn.sendall(b"\r\nDraw how many squares? ")
                input = b""
                next_mode = 9
                mode = 2

            # draw semi graphics squares in random positions
            if mode == 9:
                # clear screen
                conn.sendall(b"\x1b\x6a")
                # put in semi graphics mode
                conn.sendall(b"\x1b\x47\x34")
                
                for i in range(int(input)):
                    conn.sendall(b"\x1b\x59")
                    x = 0x20 + random.randrange(31)
                    y = 0x20 + random.randrange(14)
                    c = 128 + random.randrange(127)
                    conn.sendall(bytes(chr(y),'latin_1'))
                    conn.sendall(bytes(chr(x),'latin_1'))
                    conn.sendall(bytes(chr(c),'latin_1'))
                    
                # put in alpha only mode
                conn.sendall(b"\x1b\x47\x4e")
                
                # position cursor at bottom of screen
                conn.sendall(b"\x1b\x59")
                x = 0x20
                y = 0x20 + 15
                conn.sendall(bytes(chr(y),'latin_1'))
                conn.sendall(bytes(chr(x),'latin_1'))
                conn.sendall(b"Press <enter> to continue")
                
                mode = 2
                input = b""
                next_mode = 1
            
            # describe graphics mode
            if mode == 10:
                # get list of files
                imageFiles = []
                for file in glob.glob("*.jpg"):
                    imageFiles.append(file)
                
                conn.sendall(b"\r\nList of avaiable files:")
                i = 1
                for file in imageFiles:
                    conn.sendall(b"\r\n")
                    conn.sendall(bytes(str(i)+" ",'latin_1'))
                    conn.sendall(bytes(file,'latin_1'))
                    i = i + 1
                    
                conn.sendall(b"\r\nChoose file by number: ")
                mode = 2
                input = b""
                next_mode = 11
            
            # draw medium graphics
            if mode == 11:
                # get list of files
                imageFiles = []
                for file in glob.glob("*.jpg"):
                    imageFiles.append(file)
                
                try:
                    imageNumber = int(input) - 1
                except ValueError:
                    conn.sendall(b"\r\nError.\r\nPress <enter> to continue")
                    mode = 2
                    input = b""
                    next_mode = 1
                    pass
                    
                if imageNumber < len(imageFiles):
                    # put in medium graphics mode
                    conn.sendall(b"\x1b\x47\x4d")
                
                    im = Image.open(imageFiles[imageNumber])
                    im = im.resize((128,96), 0)
                    im = im.convert('1')
                                
                    h = 0
                    v = 0
                
                    black = 0
                    white = 0

                    while v < 96:
                        while h < 128:
                            # count contiguous black pixels
                            while h < 128:
                                a = im.getpixel((h,v))
                                if a < 128:
                                    black = black + 1
                                else:
                                    break;
                    
                                h = h + 1
                
                            # count contiguous white pixels
                        
                            while h < 128:
                                a = im.getpixel((h,v))
                                if a >= 128:
                                    white = white + 1
                                else:
                                    break;
                    
                                h = h + 1
                
                            conn.sendall(bytes(chr(0x20+black),'latin_1'))
                            conn.sendall(bytes(chr(0x20+white),'latin_1'))
                            black = 0
                            white = 0
                
                        v = v + 1
                        h = 0
                
                    conn.sendall(b"\x1b\x47\x4e")
                    conn.sendall(b"\r\nPress <enter> to continue")
                    mode = 6
                    input = b""
                    next_mode = 1
                else:
                    conn.sendall(b"\r\nFile not found")
                    conn.sendall(b"\r\nPress <enter> to continue")
                    mode = 2
                    input = b""
                    next_mode = 1
                
            # ask which page to retrieve
            if mode == 12:
                conn.sendall(b"\r\nWhich page to retrieve? ")
                input = b""
                next_mode = 13
                mode = 2
            
            # send B Protocol to ask for page
            if mode == 13:
                # request page
                bProtocol = b"\x10B" + global_block_number + b"RP" + input + b"\x03";
                checksum = calcChecksum(bProtocol)
                sendAll_print(bProtocol)
                sendAll_print(checksum)
                next_mode = 15
                mode = 14
            
            # wait for ACK
            if mode == 14:
                data = conn.recv(1024)
                if not data:
                    break
                
                if data != b'\x10':
                    print("Error: Acknowledge not recieved\n")
                    conn.sendall(b"\r\nError: Acknowledge not recieved")
                    mode = 1
                    continue

                data = conn.recv(1024)
                if not data:
                    break
                
                if data != global_block_number:
                    print("Error: Wrong block received.\n")
                    conn.sendall(b"\r\nError: Wrong block received.")
                    mode = 1
                    continue
                
                global_block_number = int(global_block_number)
                global_block_number = global_block_number + 1
                if global_block_number > 9:
                    global_block_number = 0;
                global_block_number = bytes(str(global_block_number), 'latin_1')
                
                mode = next_mode
                input = b''
                continue
            
            # Recieve data
            if mode == 15:
                # get block until <EXT>
                while True:
                    data = conn.recv(1024)
                    if not data:
                        break
                    
                    for char in data:
                        if char < 0x20:
                            print("in: " + hex(char))
                        else:
                            print("in: " + hex(char) + " " + chr(char))

                    if data == b'\x03': # ASCII <EXT>
                        input = input + data
                        break
                    
                    input = input + data
            
                # get checksum byte
                data = conn.recv(1024)
                if not data:
                    break

                for char in data:
                    if char < 0x20:
                        print("in: " + hex(char))
                    else:
                        print("in: " + hex(char) + " " + chr(char))

                checksum = calcChecksum(input)
                
                print("Calculated checksum: " + hex(checksum[0]))
                
                if checksum != data:
                    conn.sendall(b"\r\nError: checksum incorrect")
                    mode = 1
                    continue
                
                f = open("block_read.txt","wb")
                f.write(input)
                f.close()
                
                # send ASCII ACK
                conn.sendall(b"\x10"+global_block_number)
                
                conn.sendall(b"\r\nData recieved. Length: " + bytes(str(len(input)), 'latin_1'))
                mode = 1
                continue
            
            # prepare to send binary to computer
            if mode == 16:
                conn.sendall(b"\r\nThis will send a machine language program to you device.")
                conn.sendall(b"\r\nIt takes about 30 seconds.")
                conn.sendall(b"\r\nPress <enter> to begin.")
                mode = 2
                next_mode = 17
                continue
              
            # Send binary program to terminal
            if mode == 17:
                # create block header to send binary starting at $E00
                bProtocol = b"\x10B" + global_block_number + b"B\x10\x40\x10\x4e"

                with open('keyscn2.bin', mode='rb') as file:
                    fileContent = file.read()
                
                # add object code to block (follow transparency rule)
                for byte in fileContent:
                    if byte < 0x40:
                        bProtocol = bProtocol + bytes(chr(0x10),'latin_1')
                        bProtocol = bProtocol + bytes(chr(byte+0x40),'latin_1')
                    else:
                        bProtocol = bProtocol + bytes(chr(byte),'latin_1')
                
                # end block with <ETX>
                bProtocol = bProtocol + b'\x03'

                checksum = calcChecksum(bProtocol)
                sendAll_print(bProtocol)
                sendAll_print(checksum)
                
                # wait for ACK
                mode = 14
                next_mode = 18
                continue
            
            # Tell VideoTex to display page 1
            if mode == 18:
                # create block header
                bProtocol = b"\x10B" + global_block_number + b"D1\x03"
                checksum = calcChecksum(bProtocol)
                
                # send it
                sendAll_print(bProtocol)
                sendAll_print(checksum)
                
                # wait for ACK
                mode = 14
                next_mode = 19
                continue
                    
            # Tell video text to display page 2
            if mode == 19:
                # create block header
                bProtocol = b"\x10B" + global_block_number + b"D2\x03"
                checksum = calcChecksum(bProtocol)
                
                # send it
                sendAll_print(bProtocol)
                sendAll_print(checksum)
                
                # wait for ACK
                mode = 14
                next_mode = 20
                continue
                    
            # execute program at $E00
            if mode == 20:
                # create block header
                bProtocol = b"\x10B" + global_block_number + b"G\x10\x40\x10\x4e\x03"
                checksum = calcChecksum(bProtocol)
                
                # send it
                sendAll_print(bProtocol)
                sendAll_print(checksum)
                
                # end server
                mode = 0
                continue;