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I would like to send some text to a port on my machine using telnet in the Mac OS X Terminal.

I start telnet using:

telnet localhost 8080

Then I type some text. Is that text send automatically or do I have to do something to send the text?

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What is listening on port 8080? It is an address commonly used for web servers when the usual HTTP port 80 is unavailable. If it is a web server, you need to send a complete HTTP request, finished by two newlines (return characters, really). Normally, as explained by Laas below, a newline will trigger the sending of a line. –  Harald Hanche-Olsen May 20 '11 at 13:50

3 Answers 3

The answer depends on what the remote end supports:

  1. Newer Line Mode where character processing is done locally while the remote only sends and receives control packets during typing and receives whole line when entering some end-of-line char (e.g hitting ENTER).
  2. Character-at-a-time where each char is transmitted as it is typed.
  3. Old line-at-a-time - fully completed lines are transmitted.

What the remote end does with the received input, depends on the remote end. Most server processes (HTTP, SMTP, POP, IMAP) tend to wait for end-of-line (EOL, newline) char before processing input. Some others may wait for end-of-file (EOF, ^D) before starting to process the input.

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Here's a simple Python server:

#!/usr/bin/env python

import socket

TCP_IP = ''
TCP_PORT = 5005
BUFFER_SIZE = 10  # Normally 1024, but we want fast response

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((TCP_IP, TCP_PORT))

conn, addr = s.accept()
print 'Connection address:', addr
while 1:
    data = conn.recv(BUFFER_SIZE)
    if not data: break
    print "received data:", data
    conn.send(data)  # echo


Save it as server.py, and run it python server.py.

Then try to connect using the terminal

telnet 5005

Then just type anything and press return

The server print the data in the console and send it back to you.

That way, you'll know what you have to do to send data via telnet.

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Try using send command after you've opened connection to the destination host.

send "some text"

For more information about send see man telnet

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I tried, but I just get a new line when I press enter after it. –  Jonas May 20 '11 at 12:12

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