simple HTTP client c recv() blocks - c

Question

I am try to write simple HTTP client with c ,
when i execute my program some time I gets data from website some time not.
to be specific recv() blocks, and the connection shutdown.
what the best way to deal with this problem ? I still want to get the website data.
ZeroMemory( &hints, sizeof(hints) );
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
// Resolve the server address and port
if (iResult = getaddrinfo(s1, "http", &hints, &result)) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Attempt to connect to an address until one succeeds
for(ptr=result; ptr != NULL ;ptr=ptr->ai_next) {
// Create a SOCKET for connecting to server
ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype,
ptr->ai_protocol);
if (ConnectSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
WSACleanup();
return 1;
}
iResult = connect( ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
if (iResult == SOCKET_ERROR) {
closesocket(ConnectSocket);
ConnectSocket = INVALID_SOCKET;
continue;
}
break;
}
freeaddrinfo(result);
if (ConnectSocket == INVALID_SOCKET) {
printf("Unable to connect to server!\n");
WSACleanup();
return 1;
}
// Send an initial buffer
iResult = send( ConnectSocket, sendbuf, (int)strlen(sendbuf), 0 );
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// shutdown the connection since no more data will be sent
iResult = shutdown(ConnectSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// Receive until the peer closes the connection
do {
iResult = recv(ConnectSocket, recvbuf, recvbuflen-1, 0);
if ( iResult > 0 ) {
flag = 1;
recvbuf[iResult] = '\0';
printf("%s\n",recvbuf);
}
else if ( iResult == 0 ) {
if(!flag) {
printf("conection close before recv data\n");
} else {
printf("conection close\n");
break;
}
}
else {
printf("recv failed with error: %d\n", WSAGetLastError());
}
} while(iResult>1);
// cleanup
closesocket(ConnectSocket);
WSACleanup();
return 0;
}
i've used HTTP protocol concept and sent to each url i've tried in this templet: sendbuf ="GET /[url path] HTTP 1.0/r/nHost:[www.pure_url.com]/r/n/r/n"
edit: I've tried [DaSourcerer advise] , changed to HTTP/1.1 and added Connection: close , still some time i get the data some times not.
also I added:
int tcp_timeout=10000;
unsigned int sz = sizeof(tcp_timeout);
setsockopt(ConnectSocket, SOL_SOCKET, SO_RCVTIMEO,
(char*)&tcp_timeout, sz);
this idea didn't help.

Answer 1

I think your timeouts are too strict. Your sent headers will also provoke servers to wait for further input. Try this:
GET /path HTTP/1.1
Host: example.com
Connection: close
It also bears mentioning that Host is a header introduced in HTTP/1.1. It has no meaning in HTTP/1.0. You may also be interested into RFC 7230, section 3.3.3 as you are almost certainly going to encounter chunk-encoded messages in HTTP/1.1. Don't worry, though: it can be parsed with a simple state machine.