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c++ - Winsock2,客户端-服务器通信——轮流发送/接收

转载 作者:行者123 更新时间:2023-12-01 14:03:25 25 4
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我想编写一个客户端/服务器应用程序,客户端和服务器可以在其中交换消息。

Client site communication:

send
recv
send
recv

Server site communication:

recv
send
recv
send
但是,我有一个问题,因为只有一条消息是发送/接收。之后,套接字关闭,不再发送消息。出了什么问题以及如何解决这个问题?谢谢你。
服务器代码:
#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_PORT "27501"
#define SIZE 1024

int SendAllToClient(SOCKET ClientSocket, char *buffer)
{
int iSendResult;


int total = 0, len = 1024;
int bytesleft = 1024;

while( total < len )
{
iSendResult = send( ClientSocket, buffer, 1024, NULL);

if (iSendResult == SOCKET_ERROR)
{
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
total += iSendResult;
bytesleft -= iSendResult;
}
printf("Bytes sent: %d\n", iSendResult);

return total<len?- 1: 1;
}

char *ReadFromClient(SOCKET ConnectSocket)
{
int iResult;
char *buffer = new char[1024];
memset(buffer, 0, 1024);

do
{
iResult = recv(ConnectSocket, buffer, 1024, 0);
if ( iResult > 0 )
printf("Bytes received: %d\n", iResult);
else if ( iResult == 0 )
printf("Connection closed\n");

else
printf("recv failed with error: %d\n", WSAGetLastError());

}
while( iResult > 0 );
return buffer;
}

int main(int argc , char *argv[])
{
WSADATA wsaData;
char *buffer;

SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;

struct addrinfo *result = NULL;
struct addrinfo hints;

int sessionID;
int iResult;

// Datagram d1,d2,d3;

// 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: %d\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;
}

printf("Server is listening on localhost:%s ...\n", DEFAULT_PORT);

// Accept a client socket
SOCKADDR_IN addr;
int addrlen = sizeof(addr);

ClientSocket = accept(ListenSocket, (SOCKADDR*)&addr, &addrlen);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}

char *ip = inet_ntoa(addr.sin_addr);
int port = addr.sin_port;
printf("\nClient %s:%d connected to server\n", ip, port);

// No longer need server socket
closesocket(ListenSocket);

// shutdown the connection since we're done
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}

//read
buffer = ReadFromClient(ClientSocket);
printf("FROM CLIENT: %s\n", buffer);
//send
memset(buffer, 0, 1024);
memcpy(buffer, "Hi client, how are you?", strlen("Hi client, how are you?"));
SendAllToClient(ClientSocket, buffer);
//read
//send

// cleanup
closesocket(ClientSocket);
WSACleanup();

return 0;
}
客户端代码:
#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_PORT "27501"
#define SIZE 1024

int SendAllToServer(SOCKET ServerSocket, char *buffer)
{
int iSendResult;

int total = 0, len = 1024;
int bytesleft = 1024;

while( total < len )
{
iSendResult = send( ServerSocket, buffer, 1024, NULL);

if (iSendResult == SOCKET_ERROR)
{
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ServerSocket);
WSACleanup();
return 1;
}
total += iSendResult;
bytesleft -= iSendResult;
}
printf("Bytes sent: %d\n", iSendResult);

return total<len?- 1: 1;
}

char *ReadFromServer(SOCKET ConnectSocket)
{
int iResult;
char *buffer = new char[1024];
memset(buffer, 0, 1024);

do {
iResult = recv(ConnectSocket, buffer, 1024, 0);
if ( iResult > 0 )
printf("Bytes received: %d\n", iResult);
else if ( iResult == 0 )
printf("Connection closed\n");

else
printf("recv failed with error: %d\n", WSAGetLastError());

} while( iResult > 0 );
return buffer;
}

int main(int argc , char *argv[])
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char* buffer;
int sessionID;
int iResult;
// Datagram d1,d2;

// 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: %d\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;
}

//send
buffer = new char[1024];
memset(buffer, 0, 1024);
memcpy(buffer, "Hi server", strlen("Hi server"));
SendAllToServer(ConnectSocket, buffer);
//read
memset(buffer, 0, 1024);
buffer = ReadFromServer(ConnectSocket);
printf("FROM SERVER: %s\n", buffer);
//send
//read

// cleanup
closesocket(ConnectSocket);
WSACleanup();

return 0;
}
编辑
服务器
#include "data_types.h"
#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <string>
#include <iostream>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_PORT "27015"
#define SIZE 1024

int SendAllToClient(SOCKET ClientSocket)
{
char *buffer = new char[SIZE];
int iSendResult;
memset(buffer, 0, SIZE);

int total = 0, len = SIZE;
int bytesleft = SIZE;

while( total < len )
{
iSendResult = send( ClientSocket, buffer + total, bytesleft, NULL);

if (iSendResult == SOCKET_ERROR)
{
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
total += iSendResult;
bytesleft -= iSendResult;
}
printf("Bytes sent: %d\n", iSendResult);
delete buffer;

return total<len?- 1: 1;
}

char* ReadFromClient(SOCKET ClientSocket)
{
std::string data = "";
char *all = NULL;
char buffer[1];
int total = 0, len = SIZE;
int bytesleft = SIZE;
int iResult;
memset(buffer, 0, 1);

while(total < len)
{
if ((iResult = recv(ClientSocket, buffer, 1, 0)) == 0)
{
if (errno != 0)
{
// cleanup
closesocket(ClientSocket);
WSACleanup();
exit(1);
}
}
data = data + std::string(buffer);
total += iResult;
bytesleft -= iResult;
memset(buffer, 0, 1);
}
all = new char[data.length() + 1];
strcpy(all, data.c_str());

return all;
}

int main(int argc , char *argv[])
{
WSADATA wsaData;
char *buffer;

SOCKET ListenSocket = INVALID_SOCKET;
SOCKET ClientSocket = INVALID_SOCKET;

struct addrinfo *result = NULL;
struct addrinfo hints;

int sessionID;
int iResult;

// Datagram d1,d2,d3;

// 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: %d\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;
}

printf("Server is listening on localhost:%s ...\n", DEFAULT_PORT);

// Accept a client socket
SOCKADDR_IN addr;
int addrlen = sizeof(addr);

ClientSocket = accept(ListenSocket, (SOCKADDR*)&addr, &addrlen);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed with error: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}

char *ip = inet_ntoa(addr.sin_addr);
int port = addr.sin_port;
printf("\nClient %s:%d connected to server\n", ip, port);

// No longer need server socket
closesocket(ListenSocket);

// shutdown the connection since we're done
iResult = shutdown(ClientSocket, SD_SEND);
if (iResult == SOCKET_ERROR)
{
printf("shutdown failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}

//read
buffer = new char[1024];
memset(buffer, 0, 1024);
buffer = ReadFromClient(ClientSocket);
printf("FROM CLIENT: %s\n", buffer);

//send
memset(buffer, 0, 1024);
memcpy(buffer, "Hi client, how are you?", strlen("Hi client, how are you?"));
// Send an initial buffer
iResult = send( ClientSocket, buffer, (int)strlen(buffer), 0 );
if (iResult == SOCKET_ERROR) {
wprintf(L"send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
//read
//send

// cleanup
closesocket(ClientSocket);
WSACleanup();

return 0;
}
客户
#include "data_types.h"
#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <string>
#include <iostream>
#pragma comment (lib, "Ws2_32.lib")
#define DEFAULT_PORT "27015"
#define SIZE 1024

int SendAllToServer(SOCKET ClientSocket)
{
char *buffer = new char[SIZE];
memset(buffer, 0, SIZE);

int total = 0, len = SIZE;
int bytesleft = SIZE, iSendResult;

while( total < len )
{
iSendResult = send( ClientSocket, buffer + total, bytesleft, NULL);

if (iSendResult == SOCKET_ERROR)
{
printf("send failed with error: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
return 1;
}
total += iSendResult;
bytesleft -= iSendResult;
}
printf("Bytes sent: %d\n", iSendResult);
delete buffer;

return total<len?- 1: 1;
}

char *ReadFromServer(SOCKET ClientSocket)
{
std::string data = "";
char *all = NULL;
char buffer[1];
int total = 0, len = SIZE;
int bytesleft = SIZE;
int iResult;
memset(buffer, 0, 1);

while(total < len)
{
if ((iResult = recv(ClientSocket, buffer, 1, 0)) == 0)
{
if (errno != 0)
{
// cleanup
closesocket(ClientSocket);
WSACleanup();
exit(1);
}
}
data = data + std::string(buffer);
total += iResult;
bytesleft -= iResult;
memset(buffer, 0, 1);
}
all = new char[data.length() + 1];
strcpy(all, data.c_str());

return all;
}

int main(int argc , char *argv[])
{
WSADATA wsaData;
SOCKET ConnectSocket = INVALID_SOCKET;
struct addrinfo *result = NULL,
*ptr = NULL,
hints;
char* buffer;
int sessionID;
int iResult;
// Datagram d1,d2;

// 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: %d\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;
}

//send
buffer = new char[1024];
memset(buffer, 0, 1024);
memcpy(buffer, "Hi server, how are you?", strlen("Hi server, how are you?"));
// Send an initial buffer
iResult = send( ConnectSocket, buffer, (int)strlen(buffer), 0 );
if (iResult == SOCKET_ERROR) {
closesocket(ConnectSocket);
WSACleanup();
return 1;
}
//read
memset(buffer, 0, 1024);
// Receive until the peer closes the connection
do {

iResult = recv(ConnectSocket, buffer, 1024, 0);
if ( iResult > 0 )
wprintf(L"Bytes received: %d\n", iResult);
else if ( iResult == 0 )
wprintf(L"Connection closed\n");
else
wprintf(L"recv failed with error: %d\n", WSAGetLastError());

} while( iResult > 0 );
printf("FROM SERVER: %s\n", buffer);
//send
//read

// cleanup
closesocket(ConnectSocket);
WSACleanup();

return 0;
}

最佳答案

首要问题:

    iSendResult = send( ClientSocket, buffer, 1024, NULL);
那个 1024 应该是 bytesleft .如果您已经读取了 512 个字节,则不想再读取 512 个字节。
buffer应该是 buffer + total .如果您已经发送了 512 个字节,您不想再次发送相同的 512 个字节,您想发送其他 512 个字节。
第二题:
您的 ReadFromServer功能完全被破坏并且不遵循正确的逻辑。它只会返回 fatal error ,甚至不会尝试准确读取 1,024 个字节。它最多只能读取 1,024 个字节,然后,无论它实际读取了多少字节,都会尝试再次读取 1,024 个字节——并在同一地址覆盖它已经读取的消息的任何部分!
它应该像 send 函数一样工作,首先尝试接收 1,024 字节,如果收到的字节数少于该值,则循环,直到它恰好接收到 1,024 字节或出现 fatal error 。
第三题:
    buffer = ReadFromServer(ConnectSocket);
printf("FROM SERVER: %s\n", buffer);
不要这样做。假设服务器是恶意的,并向您发送了 1,024 个字节,这些字节不是合法的 C 样式字符串。将其传递给 printf通过 %s可能导致客户端崩溃或行为不端。始终将接收自网络的数据视为不受信任且可能具有恶意。尽管您的代码在不修复此问题的情况下也可以工作,但有一天这样做会以某种可怕的方式咬住您,并且养成这不是一个好习惯。
您还应该 delete[]完成后的缓冲区。但是你为什么要返回一个原始指针呢?您可以返回 std::string , 一个 std::vector ,或许多其他更好的机制,可以避免泄漏风险并使拷贝安全。

关于c++ - Winsock2,客户端-服务器通信——轮流发送/接收,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/62475005/

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