java CServersocket变为错误数据包

Question

我有以下问题：

• 我有一个Java客户端，使用ApacheMina框架发送字符串
• 我编写了一个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格式的数据包，mina很好地转换了字符串，因此它发送了0xC3{}
• 我还在wireshark网络查看器中检查发送的数据包，它也将0xC30x84视为数据包，一切正常
• 但是我的C服务器接收以下字节：FFFFFFC3FFFFFF84

我不知道怎么了

我的C服务器的代码：

#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

你的recvbuf是char类型，怀疑你的平台上有签名。消息的两个字节都是>；127（十进制）等被视为负数。printf（“%X”）格式说明符需要一个整数（在您的平台上，从外观上看是32位），因此数字会得到符号扩展（用字节的最高有效位填充整数的最高有效24位）

试着打印出你收到的字节数。同时将printf更改为

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

Answer 2

你对printf有问题

看着The Man

o, u, x, X

The unsigned int argument is converted to unsigned octal (o), unsigned decimal (u), or unsigned hexadecimal (x and X) notation. The letters abcdef are used for x conversions; the letters ABCDEF are used for X conversions. The precision, if any, gives the minimum number of digits that must appear; if the converted value requires fewer digits, it is padded on the left with zeros. The default precision is 1. When 0 is printed with an explicit precision 0, the output is empty.

^强调我的

因此，使用%X作为格式说明符，您的数据将被提升为unsigned int，并且您必须通过它，只选择要打印的字节：

printf("Byte %d: %X\n", outputCounter, recvbuf[outputCounter++] & 0xFF);