java - C-Server Socket 变成错误的数据包

Question

我有以下问题:

• 我有一个使用 apache mina 框架发送字符串的 Java 客户端。
• 我写了一个 C 服务器来接收字符串。
• 因此，我尝试向服务器发送一个 utf8 字符:myStringToSend = "Ä"
• 我调试了 mina 源代码以查看字节或十六进制的数据包，并且 mina 很好地转换了字符串，所以它发送了 0xC3 0x84。
• 我还在 wireshark 网络查看器中检查了发送的数据包，它还看到 0xC3 0x84 作为数据包，一切正常。
• 但我的 C 服务器收到以下字节:FFFFFFFC3FFFFFF84

不知道怎么回事？

我的C-Server代码:

#include "stdafx.h"
#include <io.h>
#include <stdio.h>
#include <winsock2.h>

#pragma comment(lib,"ws2_32.lib") //Winsock Library

#define DEFAULT_BUFLEN 512
#define TOOBIG 100000

int main(int argc, char *argv[])
{
WSADATA wsa;
int i, c, iResult, iSendResult, outputCounter;

SOCKET listenSocket = INVALID_SOCKET, clientSocket = INVALID_SOCKET;
struct sockaddr_in server, client; 
char *message;

char sendbuf[DEFAULT_BUFLEN];
unsigned char recvbuf[DEFAULT_BUFLEN];
int recvbuflen = DEFAULT_BUFLEN;

printf("\nInitialising Winsock...");
if (WSAStartup(MAKEWORD(2,2),&wsa) != NO_ERROR)
{
    printf("Failed. Error Code : %d",WSAGetLastError());
    return 1;
}
printf("Initialised.\n");     

if((listenSocket = socket(AF_INET , SOCK_STREAM , IPPROTO_TCP )) == INVALID_SOCKET) //IPv4, TCP
{
    printf("Could not create socket : %d" , WSAGetLastError());
    WSACleanup();
    return 1;
}

printf("Socket created.\n");

memset(&server, '0', sizeof(server));
memset(sendbuf, '0', sizeof(sendbuf)); 

server.sin_family = AF_INET;
//server.sin_addr.s_addr = htonl(0x7F000001); //localhost - 127.0.0.1
server.sin_addr.s_addr = inet_addr("127.0.0.1");
//server.sin_addr.s_addr = inet_addr("10.48.53.166");
server.sin_port = htons(7368); 

if( bind(listenSocket ,(struct sockaddr *)&server , sizeof(server)) == SOCKET_ERROR)
{
    printf("Bind failed with error code : %d" , WSAGetLastError());
    closesocket(listenSocket);
    WSACleanup();
    return 1;
}

puts("Bind done");

listen(listenSocket, 10); 

//Accept and incoming connection
puts("Waiting for incoming connections...");


c = sizeof(struct sockaddr_in);

message = "{\"id\":2,\"result\":{\"code\":\"999\",\"message\":\"AddPageRange StartIndex don't match Inspection Counter\"},\"Client_ID\":\"PQCS1\",\"jsonrpc\":\"2.0\",\"Protocol\":\"2H\"}";

while( (clientSocket = accept(listenSocket , (struct sockaddr *)NULL, NULL)) != INVALID_SOCKET )
{
    puts("Connection accepted");        
    do {
        iResult = recv(clientSocket, recvbuf, recvbuflen, 0);
        if ( iResult > 0 )
        {
            printf("Bytes received: %d\n", iResult);
            recvbuf[iResult] = '\0';
            outputCounter = 0;
            while(recvbuf[outputCounter] != '\0')
                printf("%X", (unsigned char)recvbuf[outputCounter++]);              
            iSendResult = send( clientSocket, message, strlen(message), 0 );
            if (iSendResult == SOCKET_ERROR)
            {
                printf("send failed with error: %d\n", WSAGetLastError());
                closesocket(clientSocket);
                WSACleanup();
                return 1;
            }
            printf("Bytes sent: %d\n", iSendResult);
        }
        else if ( iResult == 0 )
            printf("Connection closed\n");
        else
            printf("recv failed: %d\n", WSAGetLastError());
    } while( iResult > 0 );

 }
if (clientSocket == INVALID_SOCKET)
{
    printf("accept failed with error code : %d" , WSAGetLastError());
    return 1;
}
closesocket(listenSocket);
WSACleanup();

return 0;
}

Answer 1

您的 recvbuf 是怀疑在您的平台上签名的 char 类型。您消息的两个字节都> 127(十进制)，因此被视为负数。 printf("%X") 格式说明符需要一个整数(在您的平台上看起来是 32 位)，因此数字得到符号扩展(用字节的最高有效位填充整数的最高有效 24 位) .

尝试打印出您收到了多少字节。同时将您的 printf 更改为

printf("%X",  ((int)recvbuf[outputCounter++]) & 0xff);