TCP编程：struct的封包和解包

除封包和解包，还使用#pragma控制struct内存对齐，适应不同的机器，保证服务器和客户端都能在对应位置上取到对应的值。

服务器：

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <sys/wait.h>
#include <string.h>
#include <errno.h>
#include "define.h"
#define DEFAULT_PORT 6666
int main( int argc, char ** argv){
    int sockfd,acceptfd; /* 监听socket: sock_fd,数据传输socket: acceptfd */
    struct sockaddr_in my_addr; /* 本机地址信息 */
    struct sockaddr_in their_addr; /* 客户地址信息 */
    unsigned int sin_size, myport=6666, lisnum=10;
    if ((sockfd = socket(AF_INET , SOCK_STREAM, 0)) == -1) {
        perror("socket" );
        return -1;
    }
    printf("socket ok \n");
    my_addr.sin_family=AF_INET;
    my_addr.sin_port=htons(DEFAULT_PORT);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    bzero(&(my_addr.sin_zero), 0);
    if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr )) == -1) {
        perror("bind" );
        return -2;
    }
    printf("bind ok \n");
    if (listen(sockfd, lisnum) == -1) {
        perror("listen" );
        return -3;
    }
    printf("listen ok \n");
    char recvMsg[1000];
    sin_size = sizeof(my_addr);
    acceptfd = accept(sockfd,(struct sockaddr *)&my_addr,&sin_size);
    if (acceptfd < 0) {
        close(sockfd);
        printf("accept failed\n" );
        return -4;
    }
    ssize_t readLen = MyRecv(acceptfd, recvMsg, sizeof(int));
    if (readLen < 0) {
        printf("read failed\n" );
        return -1;
    }
    int len=(int)ntohl(*(int*)recvMsg);
    printf("len:%d\n",len);
    readLen = MyRecv(acceptfd, recvMsg, len);
    if (readLen < 0) {
        printf("read failed\n" );
        return -1;
    }
    char * pBuff=recvMsg;
    Pkg RecvPkg;
    int iLen=0;
    memcpy(&RecvPkg.head.num , pBuff + iLen, sizeof( int));
    iLen += sizeof(int);
    RecvPkg. head. num = ntohl(RecvPkg.head.num);
    printf("RecvPkg.head.num:%d\n" ,RecvPkg.head.num);
    memcpy(&RecvPkg.head.index , pBuff + iLen, sizeof( int));
    iLen += sizeof(int);
    RecvPkg. head. index = ntohl(RecvPkg.head.index);
    printf("RecvPkg.head.index:%d\n" ,RecvPkg.head.index);
    memcpy(&RecvPkg.content.sex , pBuff + iLen, sizeof( char));
    iLen += sizeof(char);
    printf("RecvPkg.content.sex:%c\n" ,RecvPkg.content.sex);
    memcpy(&RecvPkg.content.score , pBuff + iLen, sizeof( int));
    iLen += sizeof(int);
    RecvPkg. content.score = ntohl(RecvPkg. content.score );
    printf("RecvPkg.content.score:%d\n" ,RecvPkg.content.score);
    memcpy(&RecvPkg.content.address, pBuff + iLen, sizeof(RecvPkg.content.address ));
    iLen += sizeof(RecvPkg.content.address);
    printf("RecvPkg.content.address:%s\n" ,RecvPkg.content.address);
    memcpy(&RecvPkg.content.age , pBuff + iLen, sizeof( int));
    iLen += sizeof(int);
    RecvPkg.content.age = ntohl(RecvPkg.content.age );
    printf("RecvPkg.content.age:%d\n" ,RecvPkg.content.age);
    close(acceptfd);
    return 0;
}

客户端：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include "define.h"
#define DEFAULT_PORT 6666
int main( int argc, char * argv[]){
    int connfd = 0;
    int cLen = 0;
    struct sockaddr_in client;
    if(argc < 2){
        printf(" Uasge: clientent [server IP address]\n");
        return -1;
    }
    client.sin_family = AF_INET;
    client.sin_port = htons(DEFAULT_PORT);
    client.sin_addr.s_addr = inet_addr(argv[1]);
    connfd = socket(AF_INET, SOCK_STREAM, 0);
    if(connfd < 0){
        printf("socket() failure!\n" );
        return -1;
    }
    if(connect(connfd, (struct sockaddr*)&client, sizeof(client)) < 0){
        printf("connect() failure!\n" );
        return -1;
    }
    Pkg mypkg;
    mypkg.head.num=1;
    mypkg.head.index=10001;
    mypkg.content.sex='m';
    mypkg.content.score=90;
    char * temp="guangzhou and shanghai";
    strncpy(mypkg.content.address,temp,sizeof(mypkg.content.address));
    mypkg.content.age=18;
    ssize_t writeLen;
    int tLen=sizeof(mypkg);
    printf("tLen:%d\n" ,tLen);
    int iLen=0;
    char * pBuff= new char [1000];
    *(int*)(pBuff+iLen)= htonl(tLen);
    iLen+=sizeof( int);
    *(int*)(pBuff+iLen)= htonl(mypkg.head.num);
    iLen+=sizeof( int);
    *(int*)(pBuff+iLen)= htonl(mypkg.head.index);
    iLen+=sizeof( int);
    memcpy(pBuff+iLen,&mypkg.content.sex,sizeof( char));
    iLen+=sizeof( char);
    *(int*)(pBuff+iLen)= htonl(mypkg.content.score);
    iLen+=sizeof( int);
    memcpy(pBuff+iLen,mypkg.content.address,sizeof(mypkg.content.address));
    iLen+=(sizeof(mypkg.content.address));
    *(int*)(pBuff+iLen)= htonl(mypkg.content.age);
    iLen+=sizeof( int);
    writeLen= MySend(connfd, pBuff, iLen);
    if (writeLen < 0) {
        printf("write failed\n" );
        close(connfd);
        return 0;
    }
    else{
        printf("write sucess, writelen :%d, iLen:%d, pBuff: %s\n",writeLen,iLen,pBuff);
    }
    close(connfd);
    return 0;
}

头文件：

#pragma pack(1)
struct Header {
        int num ;//包id
        int index ;//学生编号
};
struct PkgContent {
        char sex ;//性别
        int score ;//分数
        char address [100];//地址
        int age;
};
struct Pkg {
        Header head;
        PkgContent content ;
};

int MySend( int iSock, char * pchBuf, size_t tLen){
        int iThisSend;
        unsigned int iSended=0;
        if(tLen == 0)
               return 0;
        while(iSended<tLen){
               do{
                     iThisSend = send(iSock, pchBuf, tLen-iSended, 0);
              } while((iThisSend<0) && (errno==EINTR));
               if(iThisSend < 0){
                      return(iSended);
              }
              iSended += iThisSend;
              pchBuf += iThisSend;
       }
        return(tLen);
}

int MyRecv( int iSock, char * pchBuf, size_t tCount){
        size_t tBytesRead=0;
        int iThisRead;
        while(tBytesRead < tCount){
               do{
                     iThisRead = read(iSock, pchBuf, tCount-tBytesRead);
              } while((iThisRead<0) && (errno==EINTR));
               if(iThisRead < 0){
                      return(iThisRead);
              }
               else if (iThisRead == 0)
                      return(tBytesRead);
              tBytesRead += iThisRead;
              pchBuf += iThisRead;
       }
}