#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<unistd.h>
#include<netinet/in.h>
#include <errno.h> int main(int argc, char** argv){int socketfd = 0;char sendbuf[1024];char recvbuf[1024];struct sockaddr_in server_addr;int port = 8001;int nbytes;if((socketfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == 0){fprintf(stderr, "socket Error:%s\n\a", strerror(errno));   exit(1);}bzero(&server_addr, sizeof(struct sockaddr_in));server_addr.sin_family = AF_INET;server_addr.sin_port = htons(port);server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");if((connect(socketfd, &server_addr, sizeof(server_addr))) == -1){fprintf(stderr, "connect Error:%s\n\a", strerror(errno));   exit(1);}while(1){nbytes = recv(socketfd, recvbuf, sizeof(recvbuf), 0);recvbuf[nbytes] = '\0';printf("recv data is:%s\n",recvbuf);printf("Input:");scanf("%s", sendbuf);send(socketfd, sendbuf, sizeof(sendbuf), MSG_NOSIGNAL);        }close(socketfd);exit(0);
}

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<sys/socket.h>
#include<sys/types.h>
#include<unistd.h>
#include<netinet/in.h>
#include <signal.h>
#include <errno.h>int main(int argc, char** argv){int old_fd,new_fd;struct sockaddr_in server_addr;struct sockaddr_in client_addr;char recvbuf[1024];int port = 8001;int len,nbytes;if((old_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == 0){fprintf(stderr, "socket Error:%s\n\a", strerror(errno));   exit(1);}bzero(&server_addr, sizeof(struct sockaddr_in));server_addr.sin_family = AF_INET;server_addr.sin_port = htons(port);server_addr.sin_addr.s_addr =  htonl(INADDR_ANY);if((bind(old_fd, &server_addr, sizeof(server_addr))) == -1){fprintf(stderr, "bind Error:%s\n\a", strerror(errno));   exit(1);}//listen的第二个参数backlog为内核缓存队列长度，该队列针对每个监听套接字包含两个队列：//一是未完成三次握手的，二是完成三次握手的if(listen(old_fd, 10) == -1){fprintf(stderr, "listen Error:%s\n\a", strerror(errno));   exit(1);}while(1){len = sizeof(struct sockaddr_in);if ((new_fd = accept(old_fd, (struct sockaddr *)&client_addr, &len)) == -1) {   fprintf(stderr, "Accept error:%s\n\a", strerror(errno));   exit(1);   }while(1){if (send(new_fd, "hello fredric", strlen("hello fredric"), MSG_NOSIGNAL) == -1) {   fprintf(stderr, "send error:%s\n", strerror(errno)); exit(1);   }nbytes = recv(new_fd, recvbuf, sizeof(recvbuf), 0);recvbuf[nbytes] = '\0';printf("recv data is:%s\n",recvbuf);}close(new_fd);}close(old_fd);exit(0);
}