客户端和服务器无法交换数据,因为都得到 "stuck"
Client and server can not exchange data because both get "stuck"
简介:
我研究了 blocking TCP server and blocking TCP client 的 MSDN 示例。
鉴于修改这些示例以创建简单的聊天应用程序,我想尝试一些简单的东西。
首先,我尝试实现以下内容:
- 从服务器发送消息
- 在客户端接收并显示该消息
- 发送来自客户端的响应
- 接收并显示来自客户端的响应
相关信息
对于冗长的代码,我提前表示歉意,但我坚信为客户端和服务器提交 SSCCE 对我来说是相关的,以便社区有机会解决问题。
我已尝试使代码尽可能少,但不想省略基本的错误检查。
您可以 copy/paste 都在单个 .cpp
文件中,它们应该编译并且 运行 没有问题:
服务器代码:
#undef UNICODE
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <string>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(void)
{
WSADATA wsaData;
SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;
struct addrinfo *result = NULL;
struct addrinfo hints;
int iResult;
char recvbuf[DEFAULT_BUFLEN] = "";
int recvbuflen = DEFAULT_BUFLEN;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the server address and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if ( iResult != 0 ) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Create a SOCKET for connecting to server
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
iResult = listen(ListenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// No longer need server socket,
// because I want to accept only 1 client
closesocket(ListenSocket);
// ===================== let us try to send a message...
std::string message = "Test message from server !!!";
int total = message.size();
const int messageLength = message.size();
while (iResult = send( ClientSocket,
// send only the missing part of the string, if send failed to deliver entire packet:
// we move the start of the string forward by messageLength - total
// while we send remaining number of bytes, which is held in total
message.substr(messageLength - total, total).c_str(), total, 0),
iResult > 0)
{
total -= iResult;
}
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
/* // adding this, seems to solve the problem ???
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
*/
// receive response from client...
while (iResult = recv(ClientSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=11=]', sizeof(recvbuf));
}
if(iResult < 0)
{
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
// cleanup
closesocket(ClientSocket);
WSACleanup();
getchar(); // so I can stop the console from immediately closing...
return 0;
}
客户代码:
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <string>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(int argc, char **argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char recvbuf[DEFAULT_BUFLEN] = "";
int iResult;
int recvbuflen = DEFAULT_BUFLEN;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
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
iResult = getaddrinfo("127.0.0.1", DEFAULT_PORT, &hints, &result);
if ( iResult != 0 )
{
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;
}
// Connect to server.
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;
}
// receive message from server...
while (iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=12=]', sizeof(recvbuf));
}
if(iResult < 0)
{
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// ===================== let us try to send a message...
std::string message = "Client response...";
int total = message.size();
const int messageLength = message.size();
while (iResult = send( ConnectSocket,
// send only the missing part of the string, if send failed to deliver entire packet:
// we move the start of the string forward by messageLength - total
// while we send remaining number of bytes, which is held in total
message.substr(messageLength - total, total).c_str(), total, 0),
iResult > 0)
{
total -= iResult;
}
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;
}
// cleanup
closesocket(ConnectSocket);
WSACleanup();
getchar(); // so I can stop the console from immediately closing...
return 0;
}
问题:
我已经实施了解决方案,但没有得到预期的结果。
服务器发送消息,客户端成功接收并显示它,但随后客户端无限卡住,而不是将其响应发送给服务器,这也无限阻塞了服务器。
我为解决这个问题所做的努力:
第一次尝试:
使用调试器,我在客户端的接收块之后放置了断点,只是为了确定客户端在收到第一条消息后永远不会到达那里。
我相信 while
循环应该再次调用 recv
,这应该 return 0
,从而强制循环结束。
在我点击 Continue
之后,调试器甚至没有继续显示客户端接收缓冲区的内容,而是表现出我目前无法描述的行为,因为我不是以英语为母语的人。
第二次尝试:
我也曾尝试使用 CreateThread
将服务器的接收循环放入线程中,但这也无济于事。
我也试过将客户端的接收循环放到线程中,但也失败了。
我曾尝试将客户端和服务器接收循环都放入线程中,但也失败了。
第三次尝试:
最后,我在服务器代码中添加了对shutdown( ClientSocket, SD_SEND)
的调用,你会在代码的下方找到它,它被注释掉了。
这似乎解决了问题,但我不确定这是否是正确的解决方案,因为我刚开始使用 Winsock。
问题:
- 如何绕过 "solution" 在
send
之后添加 shutdown
?
- 如果以上是唯一的方法,我应该在
recv
之后做同样的事情吗?我应该发送什么参数(SD_SEND
、SD_RECEIVE
或 SD_BOTH
)?
再次,对于冗长的 post,我深表歉意,但作为新手,我已尝试提供尽可能多的信息,以使您的任务更轻松。
在简要浏览了您的代码后,我敢猜测客户端中的以下代码块:
while (iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=10=]', sizeof(recvbuf));
}
实际上是你的问题。您提到关闭服务器端的套接字可以解决问题。对于套接字,只要套接字处于活动状态或直到数据通过,recv 调用就会阻塞,但是当套接字关闭时,您将获得 0 的 recv。
如果你只想接收 one 消息,而不是在 recv 上循环,你应该在处理完第一个 recv 后循环回 recv 调用,或者你应该在套接字上轮询先看看有没有实际可用的数据。
简介:
我研究了 blocking TCP server and blocking TCP client 的 MSDN 示例。
鉴于修改这些示例以创建简单的聊天应用程序,我想尝试一些简单的东西。
首先,我尝试实现以下内容:
- 从服务器发送消息
- 在客户端接收并显示该消息
- 发送来自客户端的响应
- 接收并显示来自客户端的响应
相关信息
对于冗长的代码,我提前表示歉意,但我坚信为客户端和服务器提交 SSCCE 对我来说是相关的,以便社区有机会解决问题。
我已尝试使代码尽可能少,但不想省略基本的错误检查。
您可以 copy/paste 都在单个 .cpp
文件中,它们应该编译并且 运行 没有问题:
服务器代码:
#undef UNICODE
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <string>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(void)
{
WSADATA wsaData;
SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;
struct addrinfo *result = NULL;
struct addrinfo hints;
int iResult;
char recvbuf[DEFAULT_BUFLEN] = "";
int recvbuflen = DEFAULT_BUFLEN;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0) {
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the server address and port
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if ( iResult != 0 ) {
printf("getaddrinfo failed with error: %d\n", iResult);
WSACleanup();
return 1;
}
// Create a SOCKET for connecting to server
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET) {
printf("socket failed with error: %ld\n", WSAGetLastError());
freeaddrinfo(result);
WSACleanup();
return 1;
}
// Setup the TCP listening socket
iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
if (iResult == SOCKET_ERROR) {
printf("bind failed with error: %d\n", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
iResult = listen(ListenSocket, SOMAXCONN);
if (iResult == SOCKET_ERROR) {
printf("listen failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET) {
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
// No longer need server socket,
// because I want to accept only 1 client
closesocket(ListenSocket);
// ===================== let us try to send a message...
std::string message = "Test message from server !!!";
int total = message.size();
const int messageLength = message.size();
while (iResult = send( ClientSocket,
// send only the missing part of the string, if send failed to deliver entire packet:
// we move the start of the string forward by messageLength - total
// while we send remaining number of bytes, which is held in total
message.substr(messageLength - total, total).c_str(), total, 0),
iResult > 0)
{
total -= iResult;
}
if (iResult == SOCKET_ERROR) {
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
/* // adding this, seems to solve the problem ???
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR) {
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
*/
// receive response from client...
while (iResult = recv(ClientSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=11=]', sizeof(recvbuf));
}
if(iResult < 0)
{
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
// cleanup
closesocket(ClientSocket);
WSACleanup();
getchar(); // so I can stop the console from immediately closing...
return 0;
}
客户代码:
#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <string>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "27015"
int __cdecl main(int argc, char **argv)
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char recvbuf[DEFAULT_BUFLEN] = "";
int iResult;
int recvbuflen = DEFAULT_BUFLEN;
// Initialize Winsock
iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if (iResult != 0)
{
printf("WSAStartup failed with error: %d\n", iResult);
return 1;
}
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
iResult = getaddrinfo("127.0.0.1", DEFAULT_PORT, &hints, &result);
if ( iResult != 0 )
{
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;
}
// Connect to server.
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;
}
// receive message from server...
while (iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=12=]', sizeof(recvbuf));
}
if(iResult < 0)
{
printf("recv failed with error: %d\n", WSAGetLastError());
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
// ===================== let us try to send a message...
std::string message = "Client response...";
int total = message.size();
const int messageLength = message.size();
while (iResult = send( ConnectSocket,
// send only the missing part of the string, if send failed to deliver entire packet:
// we move the start of the string forward by messageLength - total
// while we send remaining number of bytes, which is held in total
message.substr(messageLength - total, total).c_str(), total, 0),
iResult > 0)
{
total -= iResult;
}
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;
}
// cleanup
closesocket(ConnectSocket);
WSACleanup();
getchar(); // so I can stop the console from immediately closing...
return 0;
}
问题:
我已经实施了解决方案,但没有得到预期的结果。
服务器发送消息,客户端成功接收并显示它,但随后客户端无限卡住,而不是将其响应发送给服务器,这也无限阻塞了服务器。
我为解决这个问题所做的努力:
第一次尝试:
使用调试器,我在客户端的接收块之后放置了断点,只是为了确定客户端在收到第一条消息后永远不会到达那里。
我相信 while
循环应该再次调用 recv
,这应该 return 0
,从而强制循环结束。
在我点击 Continue
之后,调试器甚至没有继续显示客户端接收缓冲区的内容,而是表现出我目前无法描述的行为,因为我不是以英语为母语的人。
第二次尝试:
我也曾尝试使用 CreateThread
将服务器的接收循环放入线程中,但这也无济于事。
我也试过将客户端的接收循环放到线程中,但也失败了。
我曾尝试将客户端和服务器接收循环都放入线程中,但也失败了。
第三次尝试:
最后,我在服务器代码中添加了对shutdown( ClientSocket, SD_SEND)
的调用,你会在代码的下方找到它,它被注释掉了。
这似乎解决了问题,但我不确定这是否是正确的解决方案,因为我刚开始使用 Winsock。
问题:
- 如何绕过 "solution" 在
send
之后添加shutdown
? - 如果以上是唯一的方法,我应该在
recv
之后做同样的事情吗?我应该发送什么参数(SD_SEND
、SD_RECEIVE
或SD_BOTH
)?
再次,对于冗长的 post,我深表歉意,但作为新手,我已尝试提供尽可能多的信息,以使您的任务更轻松。
在简要浏览了您的代码后,我敢猜测客户端中的以下代码块:
while (iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0), iResult > 0)
{
printf("%s", recvbuf);
memset(recvbuf, '[=10=]', sizeof(recvbuf));
}
实际上是你的问题。您提到关闭服务器端的套接字可以解决问题。对于套接字,只要套接字处于活动状态或直到数据通过,recv 调用就会阻塞,但是当套接字关闭时,您将获得 0 的 recv。
如果你只想接收 one 消息,而不是在 recv 上循环,你应该在处理完第一个 recv 后循环回 recv 调用,或者你应该在套接字上轮询先看看有没有实际可用的数据。