A connection-oriented client
This example shows how to create a socket client program to connect
to a connection-oriented server in a connection-oriented design.
The client of the service (the client program) must request the
service of the server program. You can use this example to write your
own client application.
Note: By using the examples, you agree to
the terms of the Code license and disclaimer information.
/**************************************************************************/ /* This sample program provides a code for a connection-oriented client. */ /**************************************************************************/ /**************************************************************************/ /* Header files needed for this sample program */ /**************************************************************************/#include "stdio.h" #include "string.h" #include "sys/types.h" #include "sys/socket.h" #include "netinet/in.h" #include "arpa/inet.h" #include "netdb.h" /**************************************************************************/ /* Constants used by this program */ /**************************************************************************/ #define SERVER_PORT 3005 #define BUFFER_LENGTH 250 #define FALSE 0 #define SERVER_NAME "ServerHostName" /* Pass in 1 parameter which is either the */ /* address or host name of the server, or */ /* set the server name in the #define */ /* SERVER_NAME. */ void main(int argc, char *argv[]) { /***********************************************************************/ /* Variable and structure definitions. */ /***********************************************************************/ int sd=-1, rc, bytesReceived; char buffer[BUFFER_LENGTH]; char server[NETDB_MAX_HOST_NAME_LENGTH]; struct sockaddr_in serveraddr; struct hostent *hostp; /***********************************************************************/ /* A do/while(FALSE) loop is used to make error cleanup easier. The */ /* close() of the socket descriptor is only done once at the very end */ /* of the program. */ /***********************************************************************/ do { /********************************************************************/ /* The socket() function returns a socket descriptor, which represents */ /* an endpoint. The statement also identifies that the INET */ /* (Internet Protocol) address family with the TCP transport */ /* (SOCK_STREAM) will be used for this socket. */ /********************************************************************/ sd = socket(AF_INET, SOCK_STREAM, 0); if (sd < 0) { perror("socket() failed"); break; } /********************************************************************/ /* If an argument was passed in, use this as the server, otherwise */ /* use the #define that is located at the top of this program. */ /********************************************************************/ if (argc > 1) strcpy(server, argv[1]); else strcpy(server, SERVER_NAME); memset(&serveraddr, 0, sizeof(serveraddr)); serveraddr.sin_family = AF_INET; serveraddr.sin_port = htons(SERVER_PORT); serveraddr.sin_addr.s_addr = inet_addr(server); if (serveraddr.sin_addr.s_addr == (unsigned long)INADDR_NONE) { /*****************************************************************/ /* The server string that was passed into the inet_addr() */ /* function was not a dotted decimal IP address. It must */ /* therefore be the hostname of the server. Use the */ /* gethostbyname() function to retrieve the IP address of the */ /* server. */ /*****************************************************************/ hostp = gethostbyname(server); if (hostp == (struct hostent *)NULL) { printf("Host not found --> "); printf("h_errno = %d\n", h_errno); break; } memcpy(&serveraddr.sin_addr, hostp->h_addr, sizeof(serveraddr.sin_addr)); } /********************************************************************/ /* Use the connect() function to establish a connection to the */ /* server. */ /********************************************************************/ rc = connect(sd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)); if (rc < 0) { perror("connect() failed"); break; } /********************************************************************/ /* Send 250 bytes of a's to the server */ /********************************************************************/ memset(buffer, 'a', sizeof(buffer)); rc = send(sd, buffer, sizeof(buffer), 0); if (rc < 0) { perror("send() failed"); break; } /********************************************************************/ /* In this example we know that the server is going to respond with */ /* the same 250 bytes that we just sent. Since we know that 250 */ /* bytes are going to be sent back to us, we can use the */ /* SO_RCVLOWAT socket option and then issue a single recv() and */ /* retrieve all of the data. */ /* */ /* The use of SO_RCVLOWAT is already illustrated in the server */ /* side of this example, so we will do something different here. */ /* The 250 bytes of the data may arrive in separate packets, */ /* therefore we will issue recv() over and over again until all */ /* 250 bytes have arrived. */ /********************************************************************/ bytesReceived = 0; while (bytesReceived < BUFFER_LENGTH) { rc = recv(sd, & buffer[bytesReceived], BUFFER_LENGTH - bytesReceived, 0); if (rc < 0) { perror("recv() failed"); break; } else if (rc == 0) { printf("The server closed the connection\n"); break; } /*****************************************************************/ /* Increment the number of bytes that have been received so far */ /*****************************************************************/ bytesReceived += rc; } } while (FALSE); /***********************************************************************/ /* Close down any open socket descriptors */ /***********************************************************************/ if (sd != -1) close(sd); }
Parent topic: Creating a connection-oriented socket
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