到目前为止，我发现的所有示例要么只是读或写，要么就是10000行野兽，我什至不知道从哪里开始了解它们是如何工作的。
为了测试我的代码，我将浏览器指向服务器，并发送了一个简单的http请求。结果令人困惑。
例如，在某个时候GetQueuedCompletionStatus返回并且WSARecv说它读取了我发送的http响应的字节数，尽管该响应应该(并且确实)最终到达客户端，并且recvbuffer甚至没有填充这些字节。
另外，当其他浏览器关闭连接后，我也不知道何时释放缓冲区，因为在调用closesocket之后，GetQueuedCompletionStatus会不断返回几次。
此外，一旦GetQueuedCompletionStatus返回，我不知道何时有数据要读取或有数据要写入。我可以尝试两者，看看哪个失败，但这似乎很不礼貌。
为了揭示我可能对IOCP的任何误解，我编写了一些伪代码来传达我认为我的代码所做的事情:
main {
create server socket
create io completion port
while true {
accept client socket
create completion port for client socket
create recv buffer and send buffer for client
call WSARecv once with 0 bytes for whatever reason
}
}
worker thread {
while true {
wait until GetQueuedCompletionStatus returns
do something if that failed, not quite sure what (free buffers?)
if no bytes were transferred, close socket
try to recv data
try to send data
}
}
实际代码:
#include <stdio.h>
#include <stdlib.h>
#include <winsock2.h>
#define BUFFER_SIZE 1024
typedef struct {
WSAOVERLAPPED overlapped;
SOCKET socket;
WSABUF sendbuf;
WSABUF recvbuf;
char sendbuffer[BUFFER_SIZE];
char recvbuffer[BUFFER_SIZE];
} client;
DWORD WINAPI worker_thread(HANDLE iocp){
DWORD flags = 0, n = 0;
ULONG unused;
client *c;
while (1){
int ret = GetQueuedCompletionStatus(iocp, &n, &unused, (LPOVERLAPPED*)&c, INFINITE);
printf("%3d triggered\n", c->socket);
if (ret == FALSE){
printf("%3d GetQueuedCompletionStatus error %i\n", c->socket, WSAGetLastError());
continue;
}
if (c->socket == INVALID_SOCKET){
printf("error: socket already closed\n");
continue;
}
if (n == 0) {
printf("%3d disconnected\n", c->socket);
closesocket(c->socket);
c->socket = INVALID_SOCKET;
continue;
}
/* how do I know if there is data to read or data to write? */
WSARecv(c->socket, &(c->recvbuf), 1, &n, &flags, &(c->overlapped), NULL);
printf("%3d WSARecv %ld bytes\n", c->socket, n);
WSASend(c->socket, &(c->sendbuf), 1, &n, flags, &(c->overlapped), NULL);
printf("%3d WSASend %ld bytes\n", c->socket, n);
/* TODO handle partial sends */
c->sendbuf.len = 0;
}
return 0;
}
SOCKET make_server(int port){
int yes = 1;
struct sockaddr_in addr;
SOCKET sock;
WSADATA wsaData;
WSAStartup(MAKEWORD(2, 2), &wsaData);
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = htonl(INADDR_ANY);
addr.sin_port = htons(port);
sock = WSASocket(AF_INET, SOCK_STREAM, 0, NULL, 0, WSA_FLAG_OVERLAPPED);
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (const char*)yes, sizeof(yes));
bind(sock, (struct sockaddr*)&addr, sizeof(addr));
listen(sock, SOMAXCONN);
return sock;
}
int main(){
const char *text =
"HTTP/1.0 200 OK\r\n"
"Content-Length: 13\r\n"
"Content-Type: text/html\r\n"
"Connection: Close\r\n"
"\r\n"
"Hello, World!";
SOCKET server_socket = make_server(8080);
HANDLE iocp = CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, 0, 0);
CreateThread(NULL, 0, worker_thread, iocp, 0, NULL);
while (1){
DWORD flags = 0, n = 0;
client *c;
struct sockaddr_in addr;
int addrlen = sizeof(addr);
SOCKET client_socket = WSAAccept(server_socket, (struct sockaddr*)&addr, &addrlen, NULL, 0);
printf("%3d connected\n", client_socket);
CreateIoCompletionPort((HANDLE)client_socket, iocp, 0, 0);
c = (client*)calloc(1, sizeof(*c));
c->socket = client_socket;
c->sendbuf.len = strlen(text);
c->recvbuf.len = BUFFER_SIZE;
c->sendbuf.buf = c->sendbuffer;
c->recvbuf.buf = c->recvbuffer;
strcpy(c->sendbuf.buf, text);
/* for some reason I have to receive 0 bytes once */
WSARecv(c->socket, &(c->recvbuf), 1, &n, &flags, &(c->overlapped), NULL);
}
}
输出示例:
/* Browser makes two tcp connections on socket 124 and 128. */
124 connected
128 connected
/* GetQueuedCompletionStatus returned for socket 124. */
124 triggered
/* We received the browser's http request. */
124 WSARecv 375 bytes
/* Send http response to browser. */
124 WSASend 96 bytes
/* GetQueuedCompletionStatus returned again. */
124 triggered
/* This is wrong, we should not receive our response to the browser. */
/* Also we didn't even receive data here. */
/* recvbuffer still contains the http request. */
124 WSARecv 96 bytes
/* this is ok */
124 WSASend 0 bytes
124 triggered
124 disconnected
/* Why does GetQueuedCompletionStatus still return? the socket is closed! */
/* Also how can I tell when I can safely free the buffers */
/* if GetQueuedCompletionStatus keeps returning? */
-1 triggered
-1 GetQueuedCompletionStatus error 1236
-1 triggered
-1 GetQueuedCompletionStatus error 1236
/* same again for second http request */
128 triggered
128 WSARecv 375 bytes
128 WSASend 96 bytes
128 triggered
128 WSARecv 96 bytes
128 WSASend 0 bytes
128 triggered
128 disconnected
-1 triggered
-1 GetQueuedCompletionStatus error 1236
-1 triggered
-1 GetQueuedCompletionStatus error 1236
128 connected
128 triggered
128 WSARecv 375 bytes
128 WSASend 96 bytes
128 triggered
128 WSARecv 96 bytes
128 WSASend 0 bytes
128 triggered
128 disconnected
-1 triggered
-1 GetQueuedCompletionStatus error 1236
-1 triggered
-1 GetQueuedCompletionStatus error 1236
128 connected
128 triggered
128 WSARecv 289 bytes
128 WSASend 96 bytes
128 triggered
128 WSARecv 96 bytes
128 WSASend 0 bytes
128 triggered
128 disconnected
-1 triggered
-1 GetQueuedCompletionStatus error 1236
-1 triggered
-1 GetQueuedCompletionStatus error 1236
最佳答案
您的伪代码工作流应看起来更像这样:
main {
create server socket
create io completion port
create worker thread
while not done {
accept client socket
associate client socket with completion port
create recv, send, and work buffers for client
call WSARecv with >0 bytes to start filling recv buffer
if failed {
close client socket and free associated buffers
}
}
terminate worker thread
close client sockets
close server socket
}
worker thread {
while not terminated {
call GetQueuedCompletionStatus
if failed {
if failed because of IO error {
close socket and free associated buffers
}
else if not timeout {
handle error as needed
}
}
else if no bytes were transferred {
close socket and free associated buffers
}
else if IO was WSARecv {
move data from recv buffer to end of work buffer
while work buffer has a complete message {
remove message from front of work buffer, process as needed
if output to send {
if send buffer not empty {
append output to end of send buffer, will send later
}
else {
move output to send buffer
call WSASend
if failed {
close socket and free associated buffers
}
}
}
}
call WSARecv with >0 bytes to start filling recv buffer
if failed {
close socket and free associated buffers
}
}
else if IO was WSASend {
remove reported number of bytes from front of send buffer
if send buffer not empty {
call WSASend
if failed {
close socket and free associated buffers
}
}
}
}
}
我将其保留为练习，以将其转换为您的代码。