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,因为仅发送/接收一条消息。此后,关闭套接字,并且不再发送其他消息。怎么了,怎么解决?谢谢。
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;
}
答案 0 :(得分:8)
第一期:
iSendResult = send( ClientSocket, buffer, 1024, NULL);
该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。
该buffer
应该是buffer + total
。如果您已经发送了512字节,则不想再次发送相同的512字节,而是要发送 other 512字节。
第二个问题:
您的ReadFromServer
函数只是被完全破坏,没有遵循正确的逻辑。它只会在出现致命错误时返回,甚至不会尝试准确读取1,024个字节。它只会读取1,024字节,然后,无论实际读取了多少字节,它都会尝试再次读取1,024字节-并且在同一地址覆盖已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,如果接收到的字节数少于该字节,则循环执行,直到它恰好接收到1,024字节或出现致命错误为止。
第三期:
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字节(不是合法的C样式字符串)。通过printf
将其传递给%s
可能导致客户端崩溃或行为异常。始终将从网络接收的数据视为不可信和潜在的敌意。尽管您的代码可以在不解决此问题的情况下正常运行,但是有一天这样做会以某种可怕的方式咬住您,这不是一个好习惯。
使用完缓冲区后,还应该delete[]
。但是为什么仍然要返回原始指针呢?您可以返回std::string
,std::vector
或许多其他更好的机制来避免泄漏的风险并确保副本的安全性。
答案 1 :(得分:3)
实际上,您正在关闭侦听套接字,因此一旦存在接受的连接,它将不再接受:
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);
关闭侦听器将阻止进一步的连接。 另外,您在处理客户端套接字之前先将其关闭:
// 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 );
如果要发送和接收多次,则应循环读取/写入。您只做一次(并且做错了):所以您在问题中只描述了一条消息。