Demo/sockets/gopher.py

#! /usr/bin/env python3

# A simple gopher client.
#
# Usage: gopher [ [selector] host [port] ]

import sys
import os
import socket

# Default selector, host and port
DEF_SELECTOR = ''
DEF_HOST     = 'gopher.micro.umn.edu'
DEF_PORT     = 70

# Recognized file types
T_TEXTFILE  = '0'
T_MENU      = '1'
T_CSO       = '2'
T_ERROR     = '3'
T_BINHEX    = '4'
T_DOS       = '5'
T_UUENCODE  = '6'
T_SEARCH    = '7'
T_TELNET    = '8'
T_BINARY    = '9'
T_REDUNDANT = '+'
T_SOUND     = 's'

# Dictionary mapping types to strings
typename = {'0': '<TEXT>', '1': '<DIR>', '2': '<CSO>', '3': '<ERROR>', \
        '4': '<BINHEX>', '5': '<DOS>', '6': '<UUENCODE>', '7': '<SEARCH>', \
        '8': '<TELNET>', '9': '<BINARY>', '+': '<REDUNDANT>', 's': '<SOUND>'}

# Oft-used characters and strings
CRLF = '\r\n'
TAB = '\t'

# Open a TCP connection to a given host and port
def open_socket(host, port):
    if not port:
        port = DEF_PORT
    elif type(port) == type(''):
        port = int(port)
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((host, port))
    return s

# Send a selector to a given host and port, return a file with the reply
def send_request(selector, host, port):
    s = open_socket(host, port)
    s.send(selector + CRLF)
    s.shutdown(1)
    return s.makefile('r')

# Get a menu in the form of a list of entries
def get_menu(selector, host, port):
    f = send_request(selector, host, port)
    list = []
    while 1:
        line = f.readline()
        if not line:
            print('(Unexpected EOF from server)')
            break
        if line[-2:] == CRLF:
            line = line[:-2]
        elif line[-1:] in CRLF:
            line = line[:-1]
        if line == '.':
            break
        if not line:
            print('(Empty line from server)')
            continue
        typechar = line[0]
        parts = line[1:].split(TAB)
        if len(parts) < 4:
            print('(Bad line from server: %r)' % (line,))
            continue
        if len(parts) > 4:
            print('(Extra info from server: %r)' % (parts[4:],))
        parts.insert(0, typechar)
        list.append(parts)
    f.close()
    return list

# Get a text file as a list of lines, with trailing CRLF stripped
def get_textfile(selector, host, port):
    list = []
    get_alt_textfile(selector, host, port, list.append)
    return list

# Get a text file and pass each line to a function, with trailing CRLF stripped
def get_alt_textfile(selector, host, port, func):
    f = send_request(selector, host, port)
    while 1:
        line = f.readline()
        if not line:
            print('(Unexpected EOF from server)')
            break
        if line[-2:] == CRLF:
            line = line[:-2]
        elif line[-1:] in CRLF:
            line = line[:-1]
        if line == '.':
            break
        if line[:2] == '..':
            line = line[1:]
        func(line)
    f.close()

# Get a binary file as one solid data block
def get_binary(selector, host, port):
    f = send_request(selector, host, port)
    data = f.read()
    f.close()
    return data

# Get a binary file and pass each block to a function
def get_alt_binary(selector, host, port, func, blocksize):
    f = send_request(selector, host, port)
    while 1:
        data = f.read(blocksize)
        if not data:
            break
        func(data)

# A *very* simple interactive browser

# Browser main command, has default arguments
def browser(*args):
    selector = DEF_SELECTOR
    host = DEF_HOST
    port = DEF_PORT
    n = len(args)
    if n > 0 and args[0]:
        selector = args[0]
    if n > 1 and args[1]:
        host = args[1]
    if n > 2 and args[2]:
        port = args[2]
    if n > 3:
        raise RuntimeError('too many args')
    try:
        browse_menu(selector, host, port)
    except socket.error as msg:
        print('Socket error:', msg)
        sys.exit(1)
    except KeyboardInterrupt:
        print('\n[Goodbye]')

# Browse a menu
def browse_menu(selector, host, port):
    list = get_menu(selector, host, port)
    while 1:
        print('----- MENU -----')
        print('Selector:', repr(selector))
        print('Host:', host, ' Port:', port)
        print()
        for i in range(len(list)):
            item = list[i]
            typechar, description = item[0], item[1]
            print(repr(i+1).rjust(3) + ':', description, end=' ')
            if typechar in typename:
                print(typename[typechar])
            else:
                print('<TYPE=' + repr(typechar) + '>')
        print()
        while 1:
            try:
                str = input('Choice [CR == up a level]: ')
            except EOFError:
                print()
                return
            if not str:
                return
            try:
                choice = int(str)
            except ValueError:
                print('Choice must be a number; try again:')
                continue
            if not 0 < choice <= len(list):
                print('Choice out of range; try again:')
                continue
            break
        item = list[choice-1]
        typechar = item[0]
        [i_selector, i_host, i_port] = item[2:5]
        if typechar in typebrowser:
            browserfunc = typebrowser[typechar]
            try:
                browserfunc(i_selector, i_host, i_port)
            except (IOError, socket.error):
                t, v, tb = sys.exc_info()
                print('***', t, ':', v)
        else:
            print('Unsupported object type')

# Browse a text file
def browse_textfile(selector, host, port):
    x = None
    try:
        p = os.popen('${PAGER-more}', 'w')
        x = SaveLines(p)
        get_alt_textfile(selector, host, port, x.writeln)
    except IOError as msg:
        print('IOError:', msg)
    if x:
        x.close()
    f = open_savefile()
    if not f:
        return
    x = SaveLines(f)
    try:
        get_alt_textfile(selector, host, port, x.writeln)
        print('Done.')
    except IOError as msg:
        print('IOError:', msg)
    x.close()

def raw_input(prompt):
    sys.stdout.write(prompt)
    sys.stdout.flush()
    return sys.stdin.readline()

# Browse a search index
def browse_search(selector, host, port):
    while 1:
        print('----- SEARCH -----')
        print('Selector:', repr(selector))
        print('Host:', host, ' Port:', port)
        print()
        try:
            query = input('Query [CR == up a level]: ')
        except EOFError:
            print()
            break
        query = query.strip()
        if not query:
            break
        if '\t' in query:
            print('Sorry, queries cannot contain tabs')
            continue
        browse_menu(selector + TAB + query, host, port)

# "Browse" telnet-based information, i.e. open a telnet session
def browse_telnet(selector, host, port):
    if selector:
        print('Log in as', repr(selector))
    if type(port) != type(''):
        port = repr(port)
    sts = os.system('set -x; exec telnet ' + host + ' ' + port)
    if sts:
        print('Exit status:', sts)

# "Browse" a binary file, i.e. save it to a file
def browse_binary(selector, host, port):
    f = open_savefile()
    if not f:
        return
    x = SaveWithProgress(f)
    get_alt_binary(selector, host, port, x.write, 8*1024)
    x.close()

# "Browse" a sound file, i.e. play it or save it
def browse_sound(selector, host, port):
    browse_binary(selector, host, port)

# Dictionary mapping types to browser functions
typebrowser = {'0': browse_textfile, '1': browse_menu, \
        '4': browse_binary, '5': browse_binary, '6': browse_textfile, \
        '7': browse_search, \
        '8': browse_telnet, '9': browse_binary, 's': browse_sound}

# Class used to save lines, appending a newline to each line
class SaveLines:
    def __init__(self, f):
        self.f = f
    def writeln(self, line):
        self.f.write(line + '\n')
    def close(self):
        sts = self.f.close()
        if sts:
            print('Exit status:', sts)

# Class used to save data while showing progress
class SaveWithProgress:
    def __init__(self, f):
        self.f = f
    def write(self, data):
        sys.stdout.write('#')
        sys.stdout.flush()
        self.f.write(data)
    def close(self):
        print()
        sts = self.f.close()
        if sts:
            print('Exit status:', sts)

# Ask for and open a save file, or return None if not to save
def open_savefile():
    try:
        savefile = input( \
    'Save as file [CR == don\'t save; |pipeline or ~user/... OK]: ')
    except EOFError:
        print()
        return None
    savefile = savefile.strip()
    if not savefile:
        return None
    if savefile[0] == '|':
        cmd = savefile[1:].strip()
        try:
            p = os.popen(cmd, 'w')
        except IOError as msg:
            print(repr(cmd), ':', msg)
            return None
        print('Piping through', repr(cmd), '...')
        return p
    if savefile[0] == '~':
        savefile = os.path.expanduser(savefile)
    try:
        f = open(savefile, 'w')
    except IOError as msg:
        print(repr(savefile), ':', msg)
        return None
    print('Saving to', repr(savefile), '...')
    return f

# Test program
def test():
    if sys.argv[4:]:
        print('usage: gopher [ [selector] host [port] ]')
        sys.exit(2)
    elif sys.argv[3:]:
        browser(sys.argv[1], sys.argv[2], sys.argv[3])
    elif sys.argv[2:]:
        try:
            port = int(sys.argv[2])
            selector = ''
            host = sys.argv[1]
        except ValueError:
            selector = sys.argv[1]
            host = sys.argv[2]
            port = ''
        browser(selector, host, port)
    elif sys.argv[1:]:
        browser('', sys.argv[1])
    else:
        browser()

# Call the test program as a main program
test()