Usually you can do this with telnet or netcat, unless it is an HTTPS service. I will explain how to query both services.
1. HTTP
Here is how to query an HTTP service using telnet/netcat:
netcat google.com 80
This will open a connection to google.com using port 80. The connection will wait for you to perform your query:
GET / HTTP/1.0
After typing this, you need to press enter twice, as specified in the HTTP standard. After doing this, you should get a response from the server:
HTTP/1.0 200 OK
Date: Fri, 11 Dec 2009 21:59:04 GMT
Expires: -1
Cache-Control: private, max-age=0
Content-Type: text/html; charset=ISO-8859-1
Set-Cookie: PREF=ID=..............; expires=Sun, 11-Dec-2011 21:59:04 GMT; path=/; domain=.google.com
Set-Cookie: NID=29=................; expires=Sat, 12-Jun-2010 21:59:04 GMT; path=/; domain=.google.com; HttpOnly
Server: gws
X-XSS-Protection: 0
Here, you can see all of the headers and cookies sent by the server. If you want, you can also send specific headers and cookies:
GET / HTTP/1.0
Host: http://www.google.com
2. HTTPS
Now for the fun part. OpenSSL is the library that encrypts/decrypts HTTPS (SSL) traffic, allowing you to communicate securely. This is available on Linux/Mac/Windows(cygwin). The OpenSSL installation comes with the command 'openssl' which has several modes of operation. One of them, 's_client' provides you with a simple ssl client that handles all security handshaking. Here is how to perform a GET request:
openssl s_client -connect mail.google.com:443
As soon as you run this, you will see some details on the SSL handshaking. First, you will see the details of security certificate, followed by the actual certificate:
Certificate chain
0 s:/C=US/ST=California/L=Mountain View/O=Google Inc/CN=mail.google.com
i:/C=US/O=Google Inc/CN=Google Internet Authority
1 s:/C=US/O=Google Inc/CN=Google Internet Authority
i:/C=US/O=Equifax/OU=Equifax Secure Certificate Authority
---
Server certificate
-----BEGIN CERTIFICATE-----
MIIDXDCCAsWgAwIBAgIKUmX0TgADAAANmjANBgkqhkiG9w0BAQUFADBGMQswCQYD
VQQGEwJVUzETMBEGA1UEChMKR29vZ2xlIEluYzEiMCAGA1UEAxMZR29vZ2xlIElu
dGVybmV0IEF1dGhvcml0eTAeFw0wOTExMTIyMDM2MDBaFw0xMDExMTIyMDQ2MDBa
MGkxCzAJBgNVBAYTAlVTMRMwEQYDVQQIEwpDYWxpZm9ybmlhMRYwFAYDVQQHEw1N
b3VudGFpbiBWaWV3MRMwEQYDVQQKEwpHb29nbGUgSW5jMRgwFgYDVQQDEw9tYWls
Lmdvb2dsZS5jb20wgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBAKW0UD+4ExS1
6W+aPjDdBuyqJm7c3p5O0p7sZCHiTqENOiIafxWlG6oRDkm0VOZqJY0Q9jHOEA5R
szygSWuuKqRjo/gBC6iahJHK92kOTzZ5JqzVAvkC/4UOXJjyOq1i+/euE5FPpzDy
z8z1aY5fgNM1KgylBBaY6O3tmfnJyv5fAgMBAAGjggEsMIIBKDAdBgNVHQ4EFgQU
i/Te/XX4P2mk9V/jRr/wkzCFtaIwHwYDVR0jBBgwFoAUv8Aw6/VDET5nup6R+/xq
2uNrEiQwWwYDVR0fBFQwUjBQoE6gTIZKaHR0cDovL3d3dy5nc3RhdGljLmNvbS9H
b29nbGVJbnRlcm5ldEF1dGhvcml0eS9Hb29nbGVJbnRlcm5ldEF1dGhvcml0eS5j
cmwwZgYIKwYBBQUHAQEEWjBYMFYGCCsGAQUFBzAChkpodHRwOi8vd3d3LmdzdGF0
aWMuY29tL0dvb2dsZUludGVybmV0QXV0aG9yaXR5L0dvb2dsZUludGVybmV0QXV0
aG9yaXR5LmNydDAhBgkrBgEEAYI3FAIEFB4SAFcAZQBiAFMAZQByAHYAZQByMA0G
CSqGSIb3DQEBBQUAA4GBAIvbjRwrU/ssArVMt07uzh4LUjd4Zdi0Gn9ByrtBf2h1
JMItRqGh54AwGY2dmR1ffYWkP+q4IBCts3kkxUPvBf5BaqIqxuvAljN4+1yzphGr
hxYbLC8mfz0aCLnVWWclPpvP62swYPuHca6m/Og5SJeFkyf3VdTemeh0lZZO3vhf
-----END CERTIFICATE-----
subject=/C=US/ST=California/L=Mountain View/O=Google Inc/CN=mail.google.com
issuer=/C=US/O=Google Inc/CN=Google Internet Authority
This is useful if you need to download the certificate and safe it to a certificate store. After everything is displayed, you can type your GET request as before:
GET / HTTP/1.0
Everything will be decrypted and shown to you just like netcat/telnet.
