HTTP proxy in C, recv() doesn't block?
Question
I tryied to traceback the behaviour and made up this minimal code to illustrate the problem.
What I try to do is to have a persistent connection with the client( browser ) indefinetely. The idea is that the program waits for the client to request a page and then sends a static page back.
int main(){
// Set-up proxy and wait for 1 user
int sock;
proxy_listen(&sock, DEFAULT_PORT, 1);
printf("Proxy has started..\n");
puts("Waiting for user to connect..");
int sock_user = accept(sock, (struct sockaddr*)NULL, NULL);
printf("User connected.\n");
while (1){
// Receive client's request
char buff[1000];
int got = recv(sock_user, buff, sizeof(buff), 0); // IT WON'T BLOCK HERE
printf("Client sent bytes: %d\n", got);
char *resp="\HTTP/1.1 200 OK\r\n\
Content-Length: 68\r\n\
Connection: close\r\n\r\n\
<!DOCTYPE html><html><head></head><body><p>Got it!</p></body></html>\r\n";
// Send response
int sent = send(sock_user, resp, strlen(resp), 0);
printf("Proxy sent bytes: %d\n", sent);
}
return 0;
}
Output:
Proxy has started..
Waiting for user to connect..
User connected.
Client sent bytes: 1000
Proxy sent bytes: 145
Client sent bytes: 416
Proxy sent bytes: 145
Client sent bytes: 0
Proxy sent bytes: 145
Client sent bytes: 0
The problem is that the loop doesn't pause on recv but instead goes on and on and eventually the program stops. Why is that?
Setting close to keep-alive in the response seems to solve this. I assume the server side has closed the connection after the first response. If that is the case, shouldn't recv() give me an error? Why does it give back 0 if I want it to block if there is zero data in the socket?
1 answers
solution1
1 2013-10-22 23:54:21
recv() returns a value which you are completely ignoring:
- 0, end of stream: close the socket and exit the read loop.
- -1: error: unless
errnoisEAGAIN/EWOULDBLOCKthe connection is hosed: close the socket and exit the read loop.
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