#include  <unistd.h>#include  <sys/types.h>       /* basic system data types */#include  <sys/socket.h>      /* basic socket definitions */#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */#include  <arpa/inet.h>       /* inet(3) functions */

#include <stdlib.h>#include <errno.h>#include <stdio.h>#include <string.h>

#define MAXLINE 1024//typedef struct sockaddr  SA;void handle(int connfd);

int  main(int argc, char **argv){int     listenfd, connfd;int  serverPort = 6888;int listenq = 1024;    pid_t   childpid;char buf[MAXLINE];    socklen_t socklen;

struct sockaddr_in cliaddr, servaddr;    socklen = sizeof(cliaddr);

    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);    servaddr.sin_port = htons(serverPort);

    listenfd = socket(AF_INET, SOCK_STREAM, 0);if (listenfd < 0) {        perror("socket error");return -1;    }if (bind(listenfd, (struct sockaddr *) &servaddr, socklen) < 0) {        perror("bind error");return -1;    }if (listen(listenfd, listenq) < 0) {        perror("listen error");    return -1;    }    printf("echo server startup,listen on port:%d\n", serverPort);for ( ; ; )  {        connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &socklen);if (connfd < 0) {            perror("accept error");continue;        }

        sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);        printf(buf,"");        childpid = fork();if (childpid == 0) { /* child process */            close(listenfd);    /* close listening socket */            handle(connfd);   /* process the request */            exit (0);        } else if (childpid > 0)  {            close(connfd);          /* parent closes connected socket */        } else {            perror("fork error");        }    }}

void handle(int connfd){    size_t n;char    buf[MAXLINE];

for(;;) {        n = read(connfd, buf, MAXLINE);if (n < 0) {if(errno != EINTR) {                perror("read error");break;            }        }if (n == 0) {//connfd is closed by client            close(connfd);            printf("client exit\n");break;        }//client exit        if (strncmp("exit", buf, 4) == 0) {            close(connfd);            printf("client exit\n");break;        }        write(connfd, buf, n); //write maybe fail,here don't process failed error    } } 

#include  <unistd.h>#include  <sys/types.h>       /* basic system data types */#include  <sys/socket.h>      /* basic socket definitions */#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */#include  <arpa/inet.h>       /* inet(3) functions */#include <netdb.h> /*gethostbyname function */

#include <stdlib.h>#include <errno.h>#include <stdio.h>#include <string.h>

#define MAXLINE 1024

void handle(int connfd);

int main(int argc, char **argv){char * servInetAddr = "127.0.0.1";int servPort = 6888;char buf[MAXLINE];int connfd;struct sockaddr_in servaddr;

if (argc == 2) {        servInetAddr = argv[1];    }if (argc == 3) {        servInetAddr = argv[1];        servPort = atoi(argv[2]);    }if (argc > 3) {        printf("usage: echoclient <IPaddress> <Port>\n");return -1;    }

    connfd = socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));    servaddr.sin_family = AF_INET;    servaddr.sin_port = htons(servPort);    inet_pton(AF_INET, servInetAddr, &servaddr.sin_addr);

if (connect(connfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {        perror("connect error");return -1;    }    printf("welcome to echoclient\n");    handle(connfd);     /* do it all */    close(connfd);    printf("exit\n");    exit(0);}

void handle(int sockfd){char sendline[MAXLINE], recvline[MAXLINE];int n;for (;;) {if (fgets(sendline, MAXLINE, stdin) == NULL) {break;//read eof        }/*        //也可以不用标准库的缓冲流,直接使用系统函数无缓存操作        if (read(STDIN_FILENO, sendline, MAXLINE) == 0) {            break;//read eof        }*/

        n = write(sockfd, sendline, strlen(sendline));        n = read(sockfd, recvline, MAXLINE);if (n == 0) {            printf("echoclient: server terminated prematurely\n");break;        }        write(STDOUT_FILENO, recvline, n);//如果用标准库的缓存流输出有时会出现问题//fputs(recvline, stdout);    }}

gcc echoserver.c -o echoserver./echoserver

gcc echoclient.c -o echoclient./echoclient