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我有1台服务器是用Unix和C++编写的。客户端正在使用QT和随附的套接字API。在套接字之间发送消息
服务器向客户端发送345字节的数据。从服务器
发送消息:在客户端
void Moderator::testSynch(){
int type = (int) SYNCRHONIZE_M;
//Update all connected clients with info about other clients
for(int i = 0; i<nrOfClients_; i++){
const TcpSocket &clientSocket = clients_[i].getSocket();
int clientID = clients_[i].getID();
int tempType = htonl(type);
int tempClientID = htonl(clientID);
int tempNrOfClients = htonl(funNrOfClients);
clientSocket.writeData((const char*) &tempType, sizeof(tempType));
clientSocket.writeData((const char*) &tempClientID, sizeof(tempClientID));
clientSocket.writeData((const char*) &tempNrOfClients, sizeof(tempNrOfClients));
for(int j = 0; j<nrOfClients; j++){ //Send info about connectecd clients
int tempLength = (int) clients_[j].getName().length();
int tempID = clients_[j].getID();
string tempName = clients_[j].getName();
tempID = htonl(tempID);
tempLength = htonl(tempLength);
clientSocket.writeData((const char*) &tempID, sizeof(tempID));
clientSocket.writeData((const char*) &tempLength, sizeof(tempLength));
clientSocket.writeData(tempName.c_str(), (int)tempName.length());
}
}
}
bool TcpSocket::writeData(const char* buffer, int length)const{
size_t bytesLeft = length;
ssize_t bytesWritten = 0;
while((bytesWritten = write(socketFD_, buffer, bytesLeft)) > 0){
bytesLeft -= bytesWritten;
buffer += bytesWritten;
}
return bytesLeft == 0;
}
读消息:
void ChatClient::readMessage(Message &message){
if(socket_->readData((char*) &type, sizeof(type))){
if(type == SYNCRHONIZE_M){
int nrOfUsers = 0;
socket_->readData((char*) &ID_, sizeof(ID_)); //Set the client ID that server gave us
socket_->readData((char*) &nrOfUsers, sizeof(nrOfUsers));
ID_ = ntohl(ID_);
nrOfUsers = ntohl(nrOfUsers);
qDebug("%s=%d", "nrOfUsers", nrOfUsers);
message.setMessageType(SYNCRHONIZE_M);
messageOK = true;
for(int i = 0; i<nrOfUsers; i++){ //Update client with all connected users to server
int userID = 0;
int nameLength = 0;
socket_->readData((char*) &userID, sizeof(userID));
socket_->readData((char*) &nameLength, sizeof(nameLength));
userID = ntohl(userID);
nameLength = ntohl(nameLength);
if(nameLength > 0){
qDebug("%s=%d", "nameLength", nameLength);
buffer = new char[nameLength];
socket_->readData(buffer, nameLength);
message.addUser(ConnectedUser(buffer, nameLength, userID));
delete [] buffer;
}
}
}
}
}
bool TcpSocket::readData(char* buffer, int length){
int bytesLeft = length;
int bytesRead = 0;
while((bytesRead = qSocket_->read(buffer, bytesLeft)) > 0){
bytesLeft -= bytesRead;
buffer += bytesRead;
}
return bytesLeft == 0;
}
我遇到的问题是有时从服务器的整个消息不是立即可用。
例如,前45个字节在客户端可用。客户端然后尝试读取整个消息(345字节),这会导致奇怪的行为。在客户端完成读取后,立即可用下一个300字节。
在套接字之间发送消息的最佳方式是什么?另外,如何确定是否收到了整个消息?
TCP不提供任何类型的消息边界,它只是一个字节流。您需要在循环中调用read(),直到获得所有期望的数据。如果你发布了'readXXX'函数的实现,那么有人可能会提供更具体的建议。 – Barmar
检查更新的帖子。 – Carlj901
看起来很对我。什么是“怪异行为”?假设套接字处于阻塞模式,'readString'应该等待接收整个消息。如果它处于非阻塞模式,则在调用'read()'时需要检查'EWOULDBLOCK'错误。 – Barmar