c socket

浅浅的花香味﹌ 2021-12-13 14:37 186阅读 0赞

server.c  
服务端创建逻辑：

1.  建立socket(socket())
2.  绑定ip 与端口（bind()）
3.  监听客户端请求(accept())（阻塞）
4.  给客户端返回数据(send())  
    注意：通信是根据connectfd （int),可以当做是连接id,通过此id 可以找到客户端  
    fd=file description 文件描述符

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include<errno.h>
    #include <sys/types.h>
    #include<sys/socket.h>
    #include<netinet/in.h>
    
    
    
    #define LISTEN_PORT 8000
    #define MAX_BYTES_LINE 4096
    
    
    int main(int argc,char **argv){ 
    
    int sockfd,connectfd;
    int dataLen=0;
    int i_listenPort=8000;
    
    char buffer[MAX_BYTES_LINE];
    char * c_ipAddr="127.0.0.1";
    char * c_responseInfo="Hello,you are connected!\n";
    struct sockaddr_in serverAddr;
    if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1){ 
    
    printf("create server socket error:%s(errno:%d)\n",strerror(errno),errno);
        exit(0);
    }
    memset(&serverAddr,0,sizeof(serverAddr));
    serverAddr.sin_family=AF_INET;
    serverAddr.sin_addr.s_addr=htonl(INADDR_ANY);//auto get local server ip addr
    serverAddr.sin_port=htons(LISTEN_PORT);
    
    if(bind(sockfd,(struct sockaddr*) & serverAddr,sizeof(serverAddr))==-1){ 
    printf("bind socket error:%s(errno:%d)\n",strerror(errno),errno);
    exit(0);
    }
    if(listen(sockfd,10)==-1){ 
        printf("listen socket error :%s(errno:%d)\n",strerror(errno),errno);
    exit(0);
    }
    printf("waiting for client to connect\n");
    while(1){ 
        if((connectfd=accept(sockfd,(struct sockaddr *)NULL,NULL))==-1){ 
           printf("accept socket error:%s(errorno:%d)",strerror(errno),errno);
         continue;
        }
        dataLen=recv(connectfd,buffer,MAX_BYTES_LINE,0);
        if(!fork()){  //in sub process ,fork() will return 0
            if(send(connectfd,c_responseInfo,strlen(c_responseInfo),0)==-1){ 
                perror("send response error");
                close(connectfd);
                exit(0);
            }
             buffer[dataLen]='\0';
             printf(" recv msg from client connectfd: %d,\ncontent:%s\n",connectfd,buffer);
            close(connectfd);// close connection
        }
       
    }
    
    close(sockfd);
    
    
    }

client.c

客户端逻辑：

1.  建立socket
2.  连接server(connect())\\
3.  发送数据（send（））
4.  读取返回数据（recv（）)

#include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include <errno.h>
    #include <sys/types.h>
    #include <sys/socket.h>
    #include <netinet/in.h>
    
    #define MAX_BYTES_LINE 4096
    
    int main(int argc, char **argv)
    { 
    
        int sockfd, n, recv_len;
        char recvLine[MAX_BYTES_LINE], 
             sendLine[MAX_BYTES_LINE];
        char buffer[MAX_BYTES_LINE];
        char *c_ipAddr = "127.0.0.1";
        int i_port = 8000;
        struct sockaddr_in serverAddr;
        if (argc == 1)
        { 
    
            printf("this client will connect server message:ip=127.0.0.1,Prot=8000\n");
        }
    
        else if (argc == 2)
        { 
    
            c_ipAddr = argv[1];
            printf("this client will connect server message:ip=%s,port=8000\n", c_ipAddr);
        }
        else if (argc == 3)
        { 
    
            c_ipAddr = argv[1];
            i_port = atoi(argv[2]);
            printf("this client will connect server message:IP=%s,port=%d\n", c_ipAddr, i_port);
        }
        else
        { 
    
            printf(" usage:./client <ipaddress> and port\n");
            exit(0);
        }
    
    // 1. create client socket
        if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
        { 
            printf("create socket error:%s(errno:%d)\n", strerror(errno), errno);
            exit(0);
        }
    
        memset(&serverAddr, 0, sizeof(serverAddr));
        serverAddr.sin_family = AF_INET;
        serverAddr.sin_port = htons(i_port);
        if (inet_pton(AF_INET, c_ipAddr, &serverAddr.sin_addr) <= 0)// 地址转换，10进制数转二进制
        { 
            printf("inet_pton error for %s\n", argv[1]);
            exit(0);
        }
        // 2. connect to server 
        if(connect(sockfd,(struct sockaddr *)&serverAddr,sizeof(serverAddr))<0){ 
            printf("connect error :%s)errno:%d)\n",strerror(errno),errno);
            exit(0);
        }
        //3. send data to server
        printf("send msg to Server:\n");
        fgets(sendLine,MAX_BYTES_LINE,stdin);
    
        if(send(sockfd,sendLine,strlen(sendLine),0)==-1){ 
         printf("send msg error :%s(errno:%d)",strerror(errno),errno);
         exit(0);
        }
        //4, read data from server
        if((recv_len=recv(sockfd,buffer,MAX_BYTES_LINE,0))==-1){ 
            perror("recv error");
            exit(1);
        }
         buffer[recv_len]='\0';
         printf("received :%s",buffer);
         close(sockfd);
         exit(0);
        
    
    }