Please see this question as it has a couple of answers that should help you. Here is a brief snippet from the answers code:
HttpPost request = new HttpPost(serverUrl);
request.setEntity(new ByteArrayEntity(
postMessage.toString().getBytes("UTF8")));
HttpResponse response = client.execute(request);
The other answer says you can do something like this:
protected void sendJson(final String email, final String pwd) {
HttpClient client = new DefaultHttpClient();
HttpConnectionParams.setConnectionTimeout(client.getParams(), 10000); //Timeout Limit
HttpResponse response;
JSONObject json = new JSONObject();
try{
HttpPost post = new HttpPost(URL);
json.put("email", email);
json.put("password", pwd);
StringEntity se = new StringEntity( "JSON: " + json.toString());
se.setContentEncoding(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
post.setEntity(se);
response = client.execute(post);
/*Checking response */
if(response!=null){
InputStream in = response.getEntity().getContent(); //Get the data in the entity
}
catch(Exception e){
e.printStackTrace();
createDialog("Error", "Cannot Estabilish Connection");
}
}