Hello I have a program that can telnet to a host. But I cannot understand from [for c in data] part, can anyone explain it to me? Thank you very much.
[CODE] import sys, posix, time from socket import * BUFSIZE = 1024 # Telnet protocol characters IAC = chr(255) # Interpret as command DONT = chr(254) DO = chr(253) WONT = chr(252) WILL = chr(251) def main(): # Get hostname from param host = sys.argv[1] try: # Get ip from hostname hostaddr = gethostbyname(host) except error: sys.stderr.write(sys.argv[1] + ': bad host name\n') sys.exit(2) # Check param[2] as type of protocol if len(sys.argv) > 2: servname = sys.argv[2] else: # default use telnet servname = 'telnet' # If got servname as port num if '0' <= servname[:1] <= '9': # cast port num from str to int port = eval(servname) else: try: # Get port num by service name port = getservbyname(servname, 'tcp') except error: sys.stderr.write(servname + ': bad tcp service name\n') sys.exit(2) # Create a tcp socket s = socket(AF_INET, SOCK_STREAM) # Connect to server try: s.connect((host, port)) except error, msg: sys.stderr.write('connect failed: ' + repr(msg) + '\n') sys.exit(1) # Fork a proccess pid = posix.fork() # if pid == 0: # child -- read stdin, write socket while 1: line = sys.stdin.readline() s.send(line) else: # parent -- read socket, write stdout iac = 0 # Interpret next char as command opt = '' # Interpret next char as option while 1: data = s.recv(BUFSIZE) # if recv nothing then Exit program if not data: # EOF; kill child and exit sys.stderr.write( '(Closed by remote host)\n') # Call posix function kill and send signal 9 to child posix.kill(pid, 9) sys.exit(1) cleandata = '' for c in data: if opt: print ord(c) s.send(opt + c) opt = '' elif iac: iac = 0 if c == IAC: cleandata = cleandata + c elif c in (DO, DONT): if c == DO: print '(DO)', else: print '(DONT)', opt = IAC + WONT elif c in (WILL, WONT): if c == WILL: print '(WILL)', else: print '(WONT)', opt = IAC + DONT else: print '(command)', ord(c) elif c == IAC: iac = 1 print '(IAC)', else: cleandata = cleandata + c sys.stdout.write(cleandata) sys.stdout.flush() try: main() except KeyboardInterrupt: pass -- http://mail.python.org/mailman/listinfo/python-list