我做了一个小测试，从python应用程序（客户端套接字）向c ++应用程序（套接字服务器）发送一个整数，它们都是TCP流套接字。我还测试了从python中的客户端套接字向python中的服务器套接字发送相同的整数。
我做的是发送一个4字节的数组（c ++中为char），每个char都有一个右移（> gt;＆gt;）整数（python语法）：
...
[my_int >> i & 0xff for i in (24,16,8,0)]:
...
问题是当从python中的客户端套接字发送到python中的服务器套接字时，数据“到达正常”，例如，如果我发送整数1390248303
python服务器套接字首先打印接收到的字节流，然后为打印其ascii代码的每个字节打印，然后执行：
sum([l[3-i] << 8*i for i in (3,2,1,0)])
来“重建”整数，这是结果（没关系）：
RECEIVED: b'R\xdd\x81o'
82
221
129
111
RECEIVED: 1390248303
但是C ++服务器套接字，我在其中执行相同的操作，但代码中包含更多详细信息：
...
int sum = 0;
int term = 0;
for(int i = 3;i > -1;i--)
{
printf("%d\n",msg[3-i]);
term = msg[3-i];
//if (term < 0)
// term = 256 + term;
suma += term << 8*i;
};
printf("Received: %d\n",sum);
...
输出
82
-35
-127
111
Received: 1373405551
您是否看到中间的2个字节与中间的2个字节不同，对应于python输出的服务器套接字？不仅如此，如果我向他们添加256，他们就变得相同了：
-35 + 256 = 221
-127 + 256 = 129
这种行为的原因是什么？预先感谢任何提示！
以下是应用程序的代码：
python客户端套接字：
import socket
client_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
client_socket.connect(("localhost", 7000))
my_int = 1390248303
my_bytes = bytearray()
for e in [my_int >> i & 0xff for i in (24,16,8,0)]:
my_bytes.append(e)
print("To be sent:", my_bytes)
client_socket.send(my_bytes)
print("Sent:", my_bytes)
client_socket.close()
python服务器套接字：
import socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.bind(("", 7000))
server_socket.listen(5)
print("TCPServer Waiting for client on port 7000")
while 1:
client_socket, address = server_socket.accept()
print("I got a connection from ", address)
while 1:
data = client_socket.recv(32)
print("RECEIVED:",data)
l = []
for e in data:
l.append(e)
print(e)
print("RECEIVED:",sum([l[3-i] << 8*i for i in (3,2,1,0)]))
if (data == b''):
break;
break;
C ++服务器套接字：
#define WIN32_LEAN_AND_MEAN
#include <WinSock2.h>
#include <WS2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
// link with Ws2_32.lib
#pragma comment(lib, "Ws2_32.lib")
#define DEFAULT_PORT "7000"
//"27015"
#define DEFAULT_BUFFER_LENGTH 32
//512
int main() {
WSADATA wsaData;
// Initialize Winsock
int iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
if(iResult != 0)
{
printf("WSAStartup failed: %d\n", iResult);
return 1;
}
struct addrinfo *result = NULL,
hints;
ZeroMemory(&hints, sizeof(hints));
hints.ai_family = AF_INET; // Internet address family is unspecified so that either an IPv6 or IPv4 address can be returned
hints.ai_socktype = SOCK_STREAM; // Requests the socket type to be a stream socket for the TCP protocol
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_PASSIVE;
// Resolve the local address and port to be used by the server
iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
if (iResult != 0)
{
printf("getaddrinfo failed: %d\n", iResult);
WSACleanup();
return 1;
}
SOCKET ListenSocket = INVALID_SOCKET;
// Create a SOCKET for the server to listen for client connections
ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
if (ListenSocket == INVALID_SOCKET)
{
printf("Error at socket(): %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: %d", WSAGetLastError());
freeaddrinfo(result);
closesocket(ListenSocket);
WSACleanup();
return 1;
}
freeaddrinfo(result);
// To listen on a socket
if ( listen(ListenSocket, SOMAXCONN) == SOCKET_ERROR)
{
printf("listen failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
SOCKET ClientSocket;
ClientSocket = INVALID_SOCKET;
// Accept a client socket
ClientSocket = accept(ListenSocket, NULL, NULL);
if (ClientSocket == INVALID_SOCKET)
{
printf("accept failed: %d\n", WSAGetLastError());
closesocket(ListenSocket);
WSACleanup();
return 1;
}
char recvbuf[DEFAULT_BUFFER_LENGTH];
int iSendResult;
// receive until the client shutdown the connection
do {
iResult = recv(ClientSocket, recvbuf, DEFAULT_BUFFER_LENGTH, 0);
if (iResult > 0)
{
char msg[DEFAULT_BUFFER_LENGTH];
memset(&msg, 0, sizeof(msg));
strncpy(msg, recvbuf, iResult);
printf("Received: %s\n", msg);
//Here is where I implement the python code:
//sum([l[3-i] << 8*i for i in (3,2,1,0)]));
int sum = 0;
int term = 0;
for(int i = 3;i > -1;i--)
{
printf("%d\n",msg[3-i]);
term = msg[3-i];
//if (term < 0)
// term = 256 + term;
sum += term << 8*i;
};
printf("Received: %d\n",sum);
iSendResult = send(ClientSocket, recvbuf, iResult, 0);
if (iSendResult == SOCKET_ERROR)
{
printf("send failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
getchar();
return 1;
}
printf("Bytes sent: %ld\n", iSendResult);
}
else if (iResult == 0)
printf("Connection closed\n");
else
{
printf("recv failed: %d\n", WSAGetLastError());
closesocket(ClientSocket);
WSACleanup();
getchar();
return 1;
}
} while (iResult > 0);
// Free the resouces
closesocket(ListenSocket);
WSACleanup();
getchar();
//while (true){};
return 0;
}
答案 0 :(得分：0)
msg[]声明为char，不保证为unsigned。使用unsigned char。
两行
printf("%d\n",msg[3-i]);
term = msg[3-i];
强制转换为有符号整数。 %d格式为有符号整数，请使用%u。 term被声明为int，将其设为unsigned int。
答案 1 :(得分：0)
在@Ante建议之后，我更改了C ++服务器套接字中的代码，我还将recvbuf更改为unsigned char并将int从int更改为unsigned int以保持一致性（毕竟我等待接收无符号字符并“重建”unsigned int ）但它也有效地将recvbuf和sum保留原样。我留下了以前的评论。
问题是，为了表示一个如此大的整数，我实际上使用的是无符号整数，并且正在发送的字节是ascii代码，其范围是0 - 255（无符号字符的相同范围），char范围是-127 - 126。
尽管如此，套接字并不关心数据类型，它们只是发送二进制数据，因此我接收到无符号字符，当它们放入字符时它们“溢出”并变为负数（技术上这是因为two's complement我觉得有效。
关于更正后代码的更多说明：
1）这个
if (term < 0)
term = 256 + term;
不再需要（实际上我手动修复了溢出问题）。
2）我不得不使用强制转换为char *（char ），以便能够使用recv，strncpy和send将char 作为参数而不是unsigned char *。这项工作，我认为它不是hackish，因为指向char的指针和指向unsigned char的指针指向内存中相同大小的数据类型（8位）。如果这是错误的或可能导致意外或意外的行为，请纠正我。
//char recvbuf[DEFAULT_BUFFER_LENGTH];
unsigned char recvbuf[DEFAULT_BUFFER_LENGTH];
int iSendResult;
// receive until the client shutdown the connection
do {
//iResult = recv(ClientSocket, recvbuf, DEFAULT_BUFFER_LENGTH, 0);
iResult = recv(ClientSocket, (char *)recvbuf, DEFAULT_BUFFER_LENGTH, 0);
if (iResult > 0)
{
//char msg[DEFAULT_BUFFER_LENGTH];
unsigned char msg[DEFAULT_BUFFER_LENGTH];
memset(&msg, 0, sizeof(msg));
//strncpy((msg, recvbuf, iResult);
strncpy((char *)msg, (char *)recvbuf, iResult);
printf("Received: %s\n", msg);
//sum([l[3-i] << 8*i for i in (3,2,1,0)]));
//int sum = 0;
unsigned int sum = 0;
//int term = 0;
unsigned int term = 0;
for(int i = 3;i > -1;i--)
{
//printf("%d\n",msg[3-i]);
printf("%u\n",msg[3-i]);
term = msg[3-i];
sum += term << 8*i;
};
//printf("Received: %d\n",sum);
printf("Received: %u\n",sum);
//iSendResult = send(ClientSocket, recvbuf, iResult, 0);
iSendResult = send(ClientSocket, (char *) recvbuf, iResult, 0);