readme explanations
Philippe PITTOLI
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# connection init (draft)
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## how things happen
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* Service: daemon providing a feature (windowing, audio, pubsub, …)
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* Application: specific application (browser, instant messaging, …)
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* service: service name
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* index: process index (to launch a service several times)
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* version: service version
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1. Service creates a unix socket /tmp/service-index-version.sock
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2. Application connects to /tmp/service-index-version.sock
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## pure "networking" view (what should go in the sockets)
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1. Application connects to /tmp/service-index-version.sock
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1. Service acknowledges (empty message)
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# messages format
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In order to communicate between the application and the service, we use the Type-Length-Value format.
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This will be used with some conventions.
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## programming, debug
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## overview
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The format will be "type : value".
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The type will be a simple byte :
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* <0 - 15> : control, meta data
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* <16 - 127> : later use
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* <128 - 255> : application specific (windowing system, audio system, …)
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index | abbreviation | semantic
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0 | close | to close the communication between the application and the service
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1 | message | to send data
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2 | error | to send an error message
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3 | ack | to send an acknowledgment
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@ -0,0 +1,109 @@
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# the problem
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End-user applications are huge, with tons of libraries used and are a pain in the ass to maintain.
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Libraries are huge, with a lot of things happening, with changes that break everything on a regular basis, with almost each time very few people working on it.
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# how to change that ?
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**Network protocols**
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Network protocols are awesome: very few changes, well documented, programming language agnostics.
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Don't (just) write libraries, write applications !
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Your need a functionality in your application, why do you have to code it ?
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Just ask a service !
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**Example**
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You want to download a file, you will always have the same input: a string corresponding to the file to get, such as _ftp://example.com/file.txt_.
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You don't have to worry about the protocol to use in your own application, the burden is on the dedicated *downloading* service.
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# benefits
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**Awesome abstractions**.
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You will be able to do things without any code.
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* applications don't have to know if the services they use is on the network or on your own computer
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* applications don't need to change anything to handle new protocols, no recompilation
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* applications can be statically compiled, the memory footprint should be extremely low (yes, even for a browser)
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**Simple applications**.
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You only need to code the specific code of your own application.
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The only thing your application should have to take care is its functionality, and to communicate to services providing abstractions.
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**Consistency**.
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Everything will be developed in the same repository: same coding standards, changes will be tested on every provided applications…
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**Code review**.
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We should always try to provide new abstractions, reducing the code needed in both services and end-user applications.
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To that end, code review is a must.
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# Application and services
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- Services: daemons providing a feature (windowing, audio, network, input, pubsub, …)
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- Applications: end-user applications (browser, mail user agent, instant messaging app, …)
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#### examples
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A browser that can download everything, via every existing protocol.
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No any specific code in the browser itself and no configuration.
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You want to play a game on your rasberry pi, but it is not powerful enough, run your application on your laptop but take the inputs from the rpi (or anywhere on the network) !
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No specific code needed.
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# TODO
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Figures, a lot of them, to explain everything.
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# connection init (draft)
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## how things happen
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1. Service creates a unix socket /tmp/service-index-version.sock
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1. Application connects to /tmp/service-index-version.sock
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__legend__:
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- service: service name
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- index: process index (to launch a service several times)
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- version: service version
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# pure "networking" view (what should go in the sockets)
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#### connection
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1. Application connects to /tmp/service-index-version.sock
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1. Service acknowledges (empty message)
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#### disconnection
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1. Application sends a message "CLOSE" to the server
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#### data
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1. Application or server sends a message "DATA", no acknowledgement
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# messages format
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In order to communicate between the application and the service, we use the Type-Length-Value format.
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This will be used with some conventions.
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## programming, debug
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## overview
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The format will be "type : value".
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The type will be a simple byte :
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* <0 - 15> : control, meta data
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* <16 - 127> : later use
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* <128 - 255> : application specific (windowing system, audio system, …)
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index | abbreviation | semantic
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0 | close | to close the communication between the application and the service
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1 | connection | to connect to the service
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2 | error | to send an error message
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3 | ack | to send an acknowledgment
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4 | message | to send data
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@ -71,7 +71,7 @@ int srv_close_proc (struct process *p)
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{
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// struct msg m_ack_dis;
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// memset (&m_ack_dis, 0, sizeof (struct msg));
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// m_ack_dis.type = MSG_TYPE_ACK_DIS;
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// m_ack_dis.type = MSG_TYPE_CLOSE;
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// if (msg_write (p->proc_fd, &m_ack_dis) < 0) {
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// handle_err ("srv_close_proc", "msg_write < 0");
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@ -136,12 +136,12 @@ int app_connection (int argc, char **argv, char **env
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return 0;
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}
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// send a DIS message then close the socket
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// send a CLOSE message then close the socket
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int app_close (struct service *srv)
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{
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struct msg m;
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memset (&m, 0, sizeof (struct msg));
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m.type = MSG_TYPE_DIS;
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m.type = MSG_TYPE_CLOSE;
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if (msg_write (srv->service_fd, &m) < 0) {
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handle_err ("app_close", "msg_write < 0");
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}
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@ -5,12 +5,11 @@
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#include <stdlib.h>
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#include <string.h>
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#define MSG_TYPE_CLOSE 0
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#define MSG_TYPE_CON 1
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#define MSG_TYPE_DIS 2
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#define MSG_TYPE_ERR 3
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#define MSG_TYPE_ACK 4
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#define MSG_TYPE_DATA 5
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#define MSG_TYPE_ACK_DIS 6
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#define MSG_TYPE_ERR 2
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#define MSG_TYPE_ACK 3
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#define MSG_TYPE_DATA 4
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struct msg {
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char type;
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