I'm busy with my own http server implementation on an embedded platform. Technically the server is HTTP 1.0 compliant, and therefore it expects the the client to send the header "Connection: Keep-Alive" to keep the connection open.
The implementation looks like this. I removed the code that parses the HTTP header and performs the request, to keep the post as short as possible:
int Service_Request(int conn) {
struct ReqInfo reqinfo;
volatile int resource = 0;
int retval = 0;
Req_Result req_result = GOT_REQ;
InitReqInfo(&reqinfo);
/* while we still have HTTP requests to process */
while (req_result == GOT_REQ)
{
/* Get HTTP request, there are 3 different return values:
* GOT_REQ: we got a valid HTTP request
* TIMEOUT_REQ we timed out waiting for a request
* ERROR_REQ there was some error receiving from the socket
* usually because the connection was closed by the peer*/
req_result = Get_Request(conn, &reqinfo);
if ( req_result == TIMEOUT_REQ)
{
/* timed out waiting for the client, exit */
retval = 0;
break;
}
else if (req_result == ERROR_REQ)
{
/* some error, exit */
retval = -1;
break;
}
/* Process the request GET, PUT and POST is supported*/
if (reqinfo.method == GET)
{
/* code to handle GET*/
}
/* PUT and POST are handled in the same way */
else if ((reqinfo.method == PUT) || (reqinfo.method == POST) )
{
/* Code to handle PUT and POST*/
}
else
{
/* not supported, code should never get here */
reqinfo.status = 501;
Return_Error_Msg(conn, &reqinfo);
}
/*Diag_Msg("Client Request: \r\n");
Diag_Msg(reqinfo.clientRequest);*/
/*
* the reqinfo.keep_alive flag will be set to 1 if the
* "Connection: Keep-Alive" header was sent by the client
*/
if(reqinfo.keep_alive == 0)
{
break;
}
reqinfo.keep_alive_max--;
if(reqinfo.keep_alive_max <= 0 )
{
/*
* the connection has been reused for the maxmum amount of times, stop
*/
break;
}
/*
* If we get here, we will clear the memory used for the client request
* and go to the beginning of the while loop to receive another request
*/
Writeline(conn,"\r\n",2);
FreeReqInfo(&reqinfo);
}
FreeReqInfo(&reqinfo);
return (retval);
}
The Get_Request function looks like this:
Req_Result Get_Request(int conn, struct ReqInfo * reqinfo) {
char buffer[MAX_REQ_LINE] = {0};
int rval;
fd_set fds;
struct timeval tv;
/* Set timeout to 5 seconds if this is the first request since the client connected, wait 5 seconds
* Otherwise, wait 5ms */
if(reqinfo->first_request == 1)
{
tv.tv_sec = 5;
tv.tv_usec = 0;
reqinfo->first_request = 0;
}
else
{
tv.tv_sec = reqinfo->keep_alive_timeout;
tv.tv_usec = 0;
}
/* Loop through request headers. If we have a simple request,
then we will loop only once. Otherwise, we will loop until
we receive a blank line which signifies the end of the headers,
or until select() times out, whichever is sooner. */
do {
/* Reset file descriptor set */
FD_ZERO(&fds);
FD_SET (conn, &fds);
/* Wait until the timeout to see if input is ready */
rval = select(conn + 1, &fds, NULL, NULL, &tv);
/* Take appropriate action based on return from select() */
if ( rval < 0 )
{
Diag_Msg("Error calling select() in get_request()");
return (ERROR_REQ);
}
else if ( rval == 0 ) {
/* input not ready after timeout */
return (TIMEOUT_REQ);
}
else {
/* We have an input line waiting, so retrieve it */
memset(buffer,0,MAX_REQ_LINE - 1);
if(Readline(conn, buffer, MAX_REQ_LINE - 1) == -1)
{
return (ERROR_REQ);
}
if(reqinfo->clientRequest == NULL)
{
reqinfo->clientRequest = calloc(MAX_REQ_LINE - 1, sizeof(char));
strncpy(reqinfo->clientRequest,buffer,MAX_REQ_LINE - 1);
}
else
{
strncat(reqinfo->clientRequest,buffer,MAX_REQ_LINE - 1);
}
Trim(buffer);
if ( buffer[0] == '\0' )
break;
if ( Parse_HTTP_Header(buffer, reqinfo) )
break;
}
} while ( reqinfo->type != SIMPLE );
return (GOT_REQ);
}
To describe the workings of this server in English: The server receives the first request. It parses the headers, if it finds the "Connection: Keep-Alive" header, it sets a flag. The server proceeds to process this request. WHen it is done it checks the keep-alive flag. If it is cleared, the server closes the connection. If set the server performs a clean-up operation and the proceeds to wait for another request over the same connection. And so on.
I tested this with curl:
C:\curl>curl -v -H "Connection: Keep-Alive" --data-binary @vid1.bin 10.84.67.129/s1p0:1/vid[1-2].bin
[1/2]: 10.84.67.129/s1p0:1/vid1.bin --> <stdout>
--_curl_--10.84.67.129/s1p0:1/vid1.bin
* About to connect() to 10.84.67.129 port 80 (#0)
* Trying 10.84.67.129...
* connected
* Connected to 10.84.67.129 (10.84.67.129) port 80 (#0)
> POST /s1p0:1/vid1.bin HTTP/1.1
> User-Agent: curl/7.28.1
> Host: 10.84.67.129
> Accept: */*
> Connection: Keep-Alive
> Content-Length: 51200
> Content-Type: application/x-www-form-urlencoded
> Expect: 100-continue
>
* HTTP 1.0, assume close after body
< HTTP/1.0 100 Continue
* HTTP 1.0, assume close after body
< HTTP/1.0 200 OK
< Server: DTSVU v0.1
< Content-Type: text/html
* HTTP/1.0 connection set to keep alive!
< Connection: Keep-Alive
< Keep-Alive: timeout=5, max=10
<
* Connection #0 to host 10.84.67.129 left intact
[2/2]: 10.84.67.129/s1p0:1/vid2.bin --> <stdout>
--_curl_--10.84.67.129/s1p0:1/vid2.bin
* Connection #0 seems to be dead!
* Closing connection #0
* About to connect() to 10.84.67.129 port 80 (#0)
* Trying 10.84.67.129...
* connected
* Connected to 10.84.67.129 (10.84.67.129) port 80 (#0)
> POST /s1p0:1/vid2.bin HTTP/1.1
> User-Agent: curl/7.28.1
> Host: 10.84.67.129
> Accept: */*
> Connection: Keep-Alive
> Content-Length: 51200
> Content-Type: application/x-www-form-urlencoded
> Expect: 100-continue
>
* HTTP 1.0, assume close after body
< HTTP/1.0 100 Continue
* HTTP 1.0, assume close after body
< HTTP/1.0 200 OK
< Server: DTSVU v0.1
< Content-Type: text/html
* HTTP/1.0 connection set to keep alive!
< Connection: Keep-Alive
< Keep-Alive: timeout=5, max=10
<
* Connection #0 to host 10.84.67.129 left intact
* Closing connection #0
As you can see, curl says: Connection #0 seems to be dead! afterthefirstrequest is completed. It then proceeds to close the connection and opens a new one. I'm sure I implemented the HTTP 1.0 keep-alive functionality correctly. SO my question is: what does curl expect over the connection after the first request is completed? Why does it decide the connection is dead?
PS the above code was adapted from http://www.paulgriffiths.net/program/c/webserv.php
