通过套接字进行数据传输[TCP]如何在c/c ++中打包多个整数并使用send()recv()传输数据? [英] Data transfer over sockets[TCP] how to pack multiple integer in c/c++ and transfer the data with send() recv()?
问题描述
我正在用c/c ++在linux上制作一个基于客户端/服务器的小型游戏，我需要将玩家回合发送到服务器.
I'm making a small client/server based game, on linux in c/c++ and I need to send the player turn to the server.
这是我的问题.
我想向服务器发送两个整数，有时它可以正常工作，但是有时服务器在第一个recv()中接收到两个整数，并且卡住了它.
I want to send two integers to the server and sometimes it works perfectly, but sometimes the server receives both integer in the first recv() and its stuck.
我知道最好的方法是打包消息.问题是我不知道语法的样子.
I know that the best way is to package the messages. The problem is I don't know how the syntax should look like.
从理论上讲->玩家输入就像一个int列= 4和第二个int行= 1，我将消息打包为4 | 1或类似的内容.然后，我从客户端发送到服务器，并在服务器上对其进行编码.一个例子可能很棒，或者可能会建议如何处理这样的事情.我对套接字编程还是很陌生.
这是我的函数的样子:
客户:
#define BUFFER 512
void send_turn_to_server(int sock, int row, int column)
{
// sends row to server from player turn
char char_row[BUFFER];
sprintf(char_row, "%d", row);
char *message_from_client = char_row;
int len, bytes_sent_row;
len = strlen(message_from_client);
if (sendall(sock, message_from_client, &len) == -1)
{
perror("sendall");
printf("We only sent %d bytes because of the error!\n", len);
}
char char_column[BUFFER];
int bytes_sent_column;
//sends column from player turn
//sprintf converts the int to char
sprintf(char_column, "%d", column);
char *column_from_client = char_column;
len = strlen(column_from_client);
if (sendall(sock, column_from_client, &len) == -1)
{
perror("sendall");
printf("We only sent %d bytes because of the error!\n", len);
}
cout << "send_turn_to_server_complete" << endl;
}
在这里，我使用《 Beej网络编程指南》中的一个功能，因此可以确定整个缓冲区都已发送.
Here I use a function from Beej's Guide to Network Programming, so I can be sure the whole buffer is sent.
客户:
int sendall(int s, char *buf, int *len)
{
int total = 0; // how many bytes we've sent
int bytesleft = *len; // how many we have left to send
int n;
while (total < *len)
{
n = send(s, buf + total, bytesleft, 0);
if (n == -1)
{
break;
}
total += n;
bytesleft -= n;
}
*len = total; // return number actually sent here
return n == -1 ? -1 : 0; // return -1 on failure, 0 on success
}
服务器:
int receive_player_turn(int sock, int &int_row, int &int_column)
{
int byte_count;
char buf[BUFFER];
byte_count = recv(sock, buf, sizeof buf, 0);
cout << "The row from player: " << buf << endl;
//The C library function int atoi(const char *str) converts the string argument str to an integer (type int).
int_row = atoi(buf);
//cleans the buffer
bzero(buf, sizeof(buf));
byte_count = recv(sock, buf, sizeof buf, 0);
cout << buf << endl;
cout << "The column from player: " << buf << endl;
//converts the char string to an int
int_column = atoi(buf);
cout << endl
<< "receive player turn worked" << endl
<< "players turn was in the row " << int_row << " and in the column " << int_column + 1 << endl;
return int_row, int_column;
}
从服务器正确输出:
Player connected: SchleichsSalaticus
The row from player: 7
4
The column from player: 4
receive player turn worked
players turn was in the row 7 and in the column 5
7 4
服务器输出错误:
Player connected: SchleichsSalaticus
The row from player: 74
推荐答案
问题在于TCP是连续的流，没有消息"的开始或结束的概念，因为它不是基于消息的.
The issue is that TCP is a continuous stream, with no concept of the start or end of a "message" because it is not message-based.
大多数时候，人们使用非常简单的成帧协议" ，通过这种方式，您每次传输时都会发送一个4字节的标头，告诉接收者要读取多少字节，然后发送那么多字节作为您的消息.
Most times, people use a very simple "framing protocol" whereby you always send a 4-byte header on every transfer which tells the recipient how many bytes to read, then you send that many bytes as your message.
使用 htonl()以网络字节顺序发送4字节的标头，那么您将可以互操作.此处.
Use htonl() to send the 4-byte header in network byte order then you will be interoperable. There is a very similar example here.
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