linux - 通过recv C/C++ 通过套接字传递结构

Question

嘿，我正在尝试像这样传递它

typedef struct t_timeSliceRequest{
unsigned int processId;
unsigned int timeRequired;
int priority;
}timeSliceRequest;

struct t_timeSliceRequest request = { 1,2,1 };
sendFlag = send(socketID,(timeSliceRequest *) &request, sin_size ,0);

在服务器端

recvFlag = recv(socketID,(timeSliceRequest *) &request,sin_size,0);

但是它接收垃圾，甚至recv返回-1，请帮助

这是我完整的康德

#include<sys/socket.h>
#include<sys/types.h>
#include<string.h>
#include<stdio.h>
#include<arpa/inet.h>
#include<time.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <netinet/in.h>

enum priority_e{ high, normal, low };

typedef struct t_timeSliceRequest{
    unsigned int processId;
    unsigned int timeRequired;
    int priority;
}timeSliceRequest;

typedef struct t_TimeSliceResponse {
    timeSliceRequest original_req;

    // Unix time stamp of when process was started on server
    unsigned int time_started;

    // Waiting and running time till end of CPU bust
    unsigned int ttl;

} TimeSliceResponse;


int main(int argc, char ** argv){
    int socketID = 0, clientID = 0;
    char sendBuffer[1024], recvBuffer[1024];
    time_t time;
    struct sockaddr_in servAddr, clientAddr;
    struct t_timeSliceRequest request = {1,1,0};

memset(sendBuffer, '0', sizeof(sendBuffer));
memset(recvBuffer, '0', sizeof(recvBuffer));

fprintf(stdout,"\n\n --- Server starting up --- \n\n");
fflush(stdout);

socketID = socket(AF_INET, SOCK_STREAM, 0);
if(socketID == -1){
    fprintf(stderr, " Can't create Socket");
    fflush(stdout);
}

servAddr.sin_family = AF_INET;
servAddr.sin_port = htons(5000);
servAddr.sin_addr.s_addr = htonl(INADDR_ANY);

int bindID, sin_size, recvFlag;
bindID = bind(socketID, (struct sockaddr *)&servAddr, sizeof(servAddr)); // Casting sockaddr_in on sockaddr and binding it with socket id
if(bindID!=-1){
    fprintf(stdout," Bind SucessFull");
    fflush(stdout);
    listen(socketID,5);
    fprintf(stdout, " Server Waiting for connections\n");
    fflush(stdout);
    while(1){
        sin_size = sizeof(struct sockaddr_in);
        clientID = accept(socketID, (struct sockaddr *) &clientAddr, &sin_size);
        fprintf(stdout,"\n I got a connection from (%s , %d)", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));
        fflush(stdout);
        sin_size = sizeof(request);
        recvFlag = recv(socketID, &request,sin_size,0);
        perror("\n Err: ");
        fprintf(stdout, "\n recvFlag: %d", recvFlag);
        fprintf(stdout, "\n Time Slice request received:\n\tPid: %d \n\tTime Required: %d ", ntohs(request.processId), ntohs(request.timeRequired));
        fflush(stdout);
        snprintf(sendBuffer, sizeof(sendBuffer), "%.24s\n", ctime(&time));
        write(clientID, sendBuffer, strlen(sendBuffer));
        close(clientID);
        sleep(1);
    }
}else{
    fprintf(stdout, " Unable to Bind");
}
close(socketID);
return 0;
}

客户端代码是:

#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>

enum priority_e{ high = +1, normal = 0, low = -1};

typedef struct t_timeSliceRequest{
    unsigned int processId;
    unsigned int timeRequired;
    int priority;
}timeSliceRequest;

int main(int argc, char *argv[])
{
    int socketID = 0 /*Socket Descriptor*/, n = 0;
    char recvBuffer[1024];
    memset(recvBuffer, '0',sizeof(recvBuffer));
    struct sockaddr_in servAddr;

    struct t_timeSliceRequest request = { 1,2,high };

    if(argc!=2){
        fprintf(stderr,"\n Usage: %s <ip of server> \n",argv[0]);
        return 1;
    }

    socketID = socket(AF_INET, SOCK_STREAM, 0);
    if(socketID == -1){
        fprintf(stderr, "\n Can't create socket \n");
        return 1;
    }

    servAddr.sin_family = AF_INET;
    servAddr.sin_port = htons(5000);

    if(inet_pton(AF_INET, argv[1], &servAddr.sin_addr)==-1){
        fprintf(stderr, "\n Unable to convert given IP to Network Form \n inet_pton Error");
        return 1;
    }

    int connectFlag, sendFlag = 0;
    connectFlag = connect(socketID, (struct sockaddr *)&servAddr, sizeof(servAddr));
    if(connectFlag == -1){
       fprintf(stderr, " Connection Failed\n");
       return 1;
    }

    int sin_size = sizeof(struct t_timeSliceRequest);
    fprintf(stdout, " \n %d \n %d \n %d", request.processId, request.timeRequired, request.priority);
    sendFlag = send(socketID, &request, sin_size ,0);
    fprintf(stdout, "\nSend Flag: %d\n", sendFlag);

    n = read(socketID, recvBuffer, sizeof(recvBuffer)-1);
    recvBuffer[n] = 0;
    fprintf(stdout, "%s",recvBuffer);
    if(n < 0){
        fprintf(stderr, " Read error\n");
    }
    return 0;
}

这是完整的代码，它给出“传输端点未连接”

Answer 1

请记住，通过网络发送这样的结构可能会导致互操作性问题:

1. 如果源和目标具有不同的字节顺序，您将收到错误的数据(考虑使用 htonl 等函数将数据转换为网络字节顺序)
2. 您的结构需要打包，否则不同的编译器可以以不同的方式对齐结构的变量(请参阅 this 以了解如何对齐变量)

无论如何，ENOTCONN 都会提示在两台主机之间建立连接时出现错误。