When C++ Socket transmits network data, the data is generally a char type character array. In addition, there are some methods to transmit the data types defined by ourselves
- Custom structure
- Json serialization
- Define Class object
1. Structure
Define a structure, for example:
struct DataPack
{
int age;
string name;
};
When sending data, process the data and forcibly convert the pointer of DataPack type to the pointer of char type, as follows:
DataPack da = { 20, "anthony" };
send(cSock, (char *)&da, sizeof(da), 0);
When receiving data, define a structure of the same type to parse the string:
DataPack tmp;
int nlen = recv(sock, (char *)&tmp, 128, 0);
if (nlen > 0)
{
cout << "Received data:" << tmp.age << " " << tmp.name << endl;
}
Alternatively:
int nlen = recv(sock, recvBuf, 128, 0); // recvBuf is the buffer for receiving data
if (nlen > 0)
{
DataPack* da = (DataPack*)recvBuf; // Convert char type pointer to DataPack type pointer
cout << "Received data:" << tmp->age << " " << tmp->name << endl;
}
1.1 network data message
In order to reduce errors in data transmission and enhance stability, we can use network data message:
Similar to the message format of network protocol, the message has two parts: packet header and packet body, which are regarded as the basic unit of network message
Packet header: describes the size and function of the packet sent this time
Packet header: the data part of the packet
Next, we define a message structure for login and logout:
// The role of messages or commands in the header (login, exit)
enum CMD
{
CMD_LOGIN,
CMD_LogOut,
CMD_ERROR
};
// Baotou
struct DataHeader
{
int lenth;
int cmd;
};
// Login data
struct Login
{
char UserName[32];
char passWord[32];
};
// Login results
struct LoginSucceed
{
int result;
};
// Log out
struct LogOut
{
char UserName[32];
};
// Results of logout
struct LogOutSucceed
{
int result;
};
Each time data is sent, the packet header is sent first, and the data is sent in the data sending part
Server implementation:
// After accepting the connection from the client
cSock = accept(sock, (sockaddr*)&clientAddr, &nAddrLen);
if (INVALID_SOCKET == cSock)
{
cout << "Error, invalid client received SOCKET..." << endl;
}
cout << "New client join:" << inet_ntoa(clientAddr.sin_addr) << endl;
//5 send sends data to the client
while (true)
{
DataHeader header = {};
int nlen = recv(cSock, (char*)&header, sizeof(header), 0);
if (nlen <= 0)
{
cout << "Client exit..." << endl;
break;
}
cout << "Command received:" << header.cmd << " Data length:" << header.lenth << endl;
//Processing requests
switch (header.cmd)
{
case CMD_LOGIN:
{
Login login;
int nlen = recv(cSock, (char*)&login, sizeof(login), 0);
LoginSucceed ret = { 1 };
send(cSock, (char*)&header, sizeof(header), 0);
send(cSock, (char*)&ret, sizeof(ret), 0);
}
break;
case CMD_LogOut:
{
LogOut logout;
recv(cSock, (char*)&logout, sizeof(logout), 0);
LogOutSucceed ret = { 1 };
send(cSock, (char*)&header, sizeof(header), 0);
send(cSock, (char*)&ret, sizeof(ret), 0);
}
break;
default:
header.cmd = CMD_ERROR;
header.lenth = 0;
send(cSock, (char*)&header, sizeof(header), 0);
break;
}
}
Client implementation:
if (SOCKET_ERROR == connect(sock, (sockaddr*)&sin, sizeof(sockaddr_in)))
{
cout << "Failed to establish connection..." << endl;
}
else {
cout << "Connection established successfully..." << endl;
}
while (true)
{
string comBuf;
cin >> comBuf;
if (comBuf == "exit")
{
break;
}
else if (comBuf == "login") {
Login login = { "anthony", "chen" };
DataHeader dh = {sizeof(login), CMD_LOGIN};
//Send request command to server
send(sock, (char*)&dh, sizeof(dh), 0);
send(sock, (char*)&login, sizeof(login), 0);
//Receiving server return data
DataHeader retHeader;
LoginSucceed loginRet;
recv(sock, (char*)&retHeader, sizeof(retHeader), 0);
recv(sock, (char*)&loginRet, sizeof(loginRet), 0);
cout << "LoginSucceed: " << loginRet.result << endl;
}
else if (comBuf == "logout") {
LogOut logout = { "anthony" };
DataHeader dh = { sizeof(logout), CMD_LogOut};
//Send request command to server
send(sock, (char*)&dh, sizeof(dh), 0);
send(sock, (char*)&logout, sizeof(logout), 0);
//Receiving server return data
DataHeader retHeader;
LogOutSucceed logoutRet;
recv(sock, (char*)&retHeader, sizeof(retHeader), 0);
recv(sock, (char*)&logoutRet, sizeof(logoutRet), 0);
cout << "LogOutSucceed: " << logoutRet.result << endl;
}
else {
cout << "Invalid command, please re-enter:" << endl;
}
}
1.2 change from multiple sending and receiving messages to one sending and receiving
In order to reduce errors, we can encapsulate multiple structures by aggregation or inheritance, as follows:
// The inheritance method is used here. In addition, you can also directly define another structure in one structure
// For example: struct Login{DataHeader header; char UserName[32]; char passWord[32];}
enum CMD
{
CMD_LOGIN,
CMD_LogOut,
CMD_LOGIN_SU,
CMD_LOGOUT_SU,
CMD_ERROR
};
struct DataHeader
{
int lenth;
int cmd;
};
// Data Package
struct Login : public DataHeader
{
Login()
{
lenth = sizeof(Login);
cmd = CMD_LOGIN;
}
char UserName[32];
char passWord[32];
};
struct LoginSucceed : public DataHeader
{
LoginSucceed()
{
lenth = sizeof(LoginSucceed);
cmd = CMD_LOGIN_SU;
}
int result;
};
struct LogOut : public DataHeader
{
LogOut()
{
lenth = sizeof(LogOut);
cmd = CMD_LogOut;
}
char UserName[32];
};
struct LogOutSucceed : public DataHeader
{
LogOutSucceed()
{
lenth = sizeof(LogOutSucceed);
cmd = CMD_LOGOUT_SU;
}
int result;
};
Server implementation:
while (true)
{
/*DataHeader header = {};
int nlen = recv(cSock, (char*)&header, sizeof(header), 0);*/
Login login;
int nlen = recv(cSock, (char*)&login, sizeof(login), 0);
if (nlen <= 0)
{
cout << "Client exit..." << endl;
break;
}
//Processing requests
switch (login.cmd)
{
case CMD_LOGIN:
{
/*Login login;
recv(cSock, (char*)&login, sizeof(login), 0);*/
cout << "Command received: CMD_LOGIN" << " Data length:" << login.lenth << " UserName: " << login.UserName << " PassWord: " << login.passWord << endl;
LoginSucceed ret;
send(cSock, (char*)&ret, sizeof(ret), 0);
}
break;
case CMD_LogOut:
{
/*LogOut logout;
recv(cSock, (char*)&logout, sizeof(logout), 0);*/
cout << "Command received: CMD_LOGIN" << " Data length:" << login.lenth << " UserName: " << login.UserName << endl;
LogOutSucceed ret;
send(cSock, (char*)&ret, sizeof(ret), 0);
}
break;
default:
login.cmd = CMD_ERROR;
login.lenth = 0;
send(cSock, (char*)&login, sizeof(login), 0);
break;
}
}
client:
while (true)
{
string comBuf;
cin >> comBuf;
if (comBuf == "exit")
{
break;
}
else if (comBuf == "login") {
Login login;
strcpy(login.UserName, "anthony");
strcpy(login.passWord, "chen");
//Send request command to server
send(sock, (char*)&login, sizeof(login), 0);
//Receiving server return data
LoginSucceed loginRet;
recv(sock, (char*)&loginRet, sizeof(loginRet), 0);
cout << "LoginSucceed: " << loginRet.result << endl;
}
else if (comBuf == "logout") {
LogOut logout;
strcpy(logout.UserName, "anthony");
//Send request command to server
send(sock, (char*)&logout, sizeof(logout), 0);
//Receiving server return data
LogOutSucceed logoutRet;
recv(sock, (char*)&logoutRet, sizeof(logoutRet), 0);
cout << "LogOutSucceed: " << logoutRet.result << endl;
}
else {
cout << "Invalid command, please re-enter:" << endl;
}
}
2. Use Jason (try later)
The full name of JSON is JavaScript Object Notation, which is a lightweight data transmission format. When C + + processes JSON format data, it needs to use a third-party library. The famous one is jsoncpp. The download address is:
3. Define Class object
Similar to structure, when transferring custom object data, you can convert the type of pointer.